If at all possible try to do the complete panel. Can't emphasize that enough.
If you have to blend, being your a first timer I'll try to outline the easiest way to do it.
First prep the panel/area like normal. 800 grit, wet sand until you have removed the gloss. No more than that. If you are not sure of your progress, stop and dry an area and check. You are simply lightly sanding to remove the gloss. Do this all the way to the edge of your blend area. keep all your scratches going in one direction, meaning sand in one direction (back and forth).
At your blend area you can prep it one of several ways. If you have some 1200-1500 grit paper lightly sand the blend area carrying it out past where your last coat will be. You need the sanded blend area to extend out past where your last coat ends. If that isn't clear, say so and I'll try to explain it better.
Mask off in such a way that your blend area is fully exposed.
Spray the SS like normal. First coat stop at the the area where the regular prep and the blend area starts. Each coat extend a little farther into the blend area. Keep in mind the edge of your last coat needs to be within the blend area. Meaning there needs to still be sanded (1200-1500 grit) area on the other side of where your last coat stops.
Once finished then spray one light/medium coat of blending solvent over the blend area. Coat should extend 12" or so into the SS and extend past the blend (end of where you sprayed) Do not spray the blending solvent too heavily or it will make it run. (ask me how I know
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Read page 6 of the Tech Manual for more info.