Chris_Hamilton
Trying to be the best me, I can be
Hi all. I figured I'd do this write up as both Crash and I thought we needed to have something here on the forum to refer folks to when asking about blending. I'll try to outline the proper technique to prep, and how to do a basecoat blend. Single stage the same principle applies. In this write up we will pretend we are repairing a silver Honda Accord that received a medium sized dent on the left rear door. We will need to repair the damage and blend into the front door and rear 1/4 panel to match the existing color. Techniques outlined here will apply to any car or blend repair. This is essentially how I have done them for 25 years. Other guys may have slightly different methods but the way I will describe will produce outstanding results. Apologies for the lack of brevity. 
Part One.
1.Prep
Proper prep is very important. Any success later depends on doing the prep correctly. First thing is to pull all trim pieces that we can. In this case we will remove the door handles and the beltline molding, as well left mirror and the rear taillight. Then onto the repair. When doing the repair we want to keep the repair area as small as possible. Using tape to outline a border around the repair area helps to get you from getting sand scratches any further out from the repair than necessary. When you prime though you do not want to tape off and prime right to the tape leaving a hard edge. Extend your masking out far enough so that the primed area is contained inside the mask and you don't leave hard edges. When you block do not use too coarse a grit. This is one time when you want to use a finer grit to block with as the sand scratches coarser grits like 180 leave are hard to deal with when doing a blend. Block out in 320 dry. It is also important to put enough primer on the panel so that you only apply once and have enough millage to block it out and then wet sand it without going through.
Once you have the damage repaired and blocked out with 320, then you move onto wet sanding. First go over the repair/blocked area with 600 grit. Sand in one direction only. This is important. You are only sanding enough to remove the 320 dry scratches. Generally going over it 2X is enough. Once the primed area is sanded then you need to prep the adjacent panels. Using 800 grit wet, sand in one direction only. You are simply trying to flatten the texture. Do not try to get it completely sanded out. Don't hammer it. Check your progress often. Flattening the texture is enough. Don't worry about edges. In this case being that we are doing a silver metallic, sand the primed area with 800 as well. There is a reason for this, I will describe later.
TO be clear in our example we are sanding the rear door, as well as the front door and quarter panel completely.
After sanding everything then the final prep step is to use some sanding paste and a grey (not optional do not use maroon) Scotchbrite pad. Wet the car and the pad, apply some sanding paste to the pad and start scuffing the panels. I like to scuff in a circular motion. However you do it, be thorough. Keep the panels wet and keep the pad "full" of sanding paste. Full isn't the right word, but you want to apply it often as it is what is doing the scuffing. Using the paste also removes any road tar, or other contaminants as well.
When finished scuffing, rinse well to ensure no residue remains. Let the panels dry and then it's time to move onto the next step.
Mask the car off. A couple of tips. When you have a wheel opening, instead of covering the tire, back mask the wheel opening shut. This will go a long way to cutting down on trash in the finish. Anything you can back mask you should. In our example we are masking off the entire car except for the front and rear door as well as the 1/4 panel. I like to outline everything in paper, then come back and plastic the whole vehicle. Then trim the plastic and tape the masking paper to the plastic. Some will just outline in tape and use plastic only. However works for you. Keep your masking neat and tight. If you have trim that is difficult to remove you can do something called a "pull off". With a pull off instead of starting at an edge like on a beltline molding, you leave a 1/4-3/8" gap. Do all your masking. When finished you would then tape that edge. When you tape it do it in such a way so that when finished clearing you can simply pull off that final tape while the clear is wet. Doing it this way leaves very little edge. Often no edge at all.
Once masked you are ready to wipe it down with W&G remover. You can refer to the sticky on how to use W&G remover for more info. I will add a few things since I have modified my technique since writing that. Because of the sanding paste scuffing, the car should be clean enough that you can use only solvent based W&G remover. I like using a sprayer like the USC pump sprayer and spray the W&G remover on the panels, then wipe them off. It is important that you use a dedicated paint prep wiper. There are a lot of them. They are marketed as lint free wipes. The best value for the money is the Axalta maintenance wipes. They actually work better than Axalta's dedicated paint wiper. The maintenance wipes are nearly lint free. More so than the dedicated wipes. I think the part number for the Axalta's is E-4584.
Part Two to follow.
Part One.
1.Prep
Proper prep is very important. Any success later depends on doing the prep correctly. First thing is to pull all trim pieces that we can. In this case we will remove the door handles and the beltline molding, as well left mirror and the rear taillight. Then onto the repair. When doing the repair we want to keep the repair area as small as possible. Using tape to outline a border around the repair area helps to get you from getting sand scratches any further out from the repair than necessary. When you prime though you do not want to tape off and prime right to the tape leaving a hard edge. Extend your masking out far enough so that the primed area is contained inside the mask and you don't leave hard edges. When you block do not use too coarse a grit. This is one time when you want to use a finer grit to block with as the sand scratches coarser grits like 180 leave are hard to deal with when doing a blend. Block out in 320 dry. It is also important to put enough primer on the panel so that you only apply once and have enough millage to block it out and then wet sand it without going through.
Once you have the damage repaired and blocked out with 320, then you move onto wet sanding. First go over the repair/blocked area with 600 grit. Sand in one direction only. This is important. You are only sanding enough to remove the 320 dry scratches. Generally going over it 2X is enough. Once the primed area is sanded then you need to prep the adjacent panels. Using 800 grit wet, sand in one direction only. You are simply trying to flatten the texture. Do not try to get it completely sanded out. Don't hammer it. Check your progress often. Flattening the texture is enough. Don't worry about edges. In this case being that we are doing a silver metallic, sand the primed area with 800 as well. There is a reason for this, I will describe later.
TO be clear in our example we are sanding the rear door, as well as the front door and quarter panel completely.
After sanding everything then the final prep step is to use some sanding paste and a grey (not optional do not use maroon) Scotchbrite pad. Wet the car and the pad, apply some sanding paste to the pad and start scuffing the panels. I like to scuff in a circular motion. However you do it, be thorough. Keep the panels wet and keep the pad "full" of sanding paste. Full isn't the right word, but you want to apply it often as it is what is doing the scuffing. Using the paste also removes any road tar, or other contaminants as well.
When finished scuffing, rinse well to ensure no residue remains. Let the panels dry and then it's time to move onto the next step.
Mask the car off. A couple of tips. When you have a wheel opening, instead of covering the tire, back mask the wheel opening shut. This will go a long way to cutting down on trash in the finish. Anything you can back mask you should. In our example we are masking off the entire car except for the front and rear door as well as the 1/4 panel. I like to outline everything in paper, then come back and plastic the whole vehicle. Then trim the plastic and tape the masking paper to the plastic. Some will just outline in tape and use plastic only. However works for you. Keep your masking neat and tight. If you have trim that is difficult to remove you can do something called a "pull off". With a pull off instead of starting at an edge like on a beltline molding, you leave a 1/4-3/8" gap. Do all your masking. When finished you would then tape that edge. When you tape it do it in such a way so that when finished clearing you can simply pull off that final tape while the clear is wet. Doing it this way leaves very little edge. Often no edge at all.
Once masked you are ready to wipe it down with W&G remover. You can refer to the sticky on how to use W&G remover for more info. I will add a few things since I have modified my technique since writing that. Because of the sanding paste scuffing, the car should be clean enough that you can use only solvent based W&G remover. I like using a sprayer like the USC pump sprayer and spray the W&G remover on the panels, then wipe them off. It is important that you use a dedicated paint prep wiper. There are a lot of them. They are marketed as lint free wipes. The best value for the money is the Axalta maintenance wipes. They actually work better than Axalta's dedicated paint wiper. The maintenance wipes are nearly lint free. More so than the dedicated wipes. I think the part number for the Axalta's is E-4584.
Part Two to follow.
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