I had some questions regarding epoxy primer. I'm cleaning the floorboards/undercarriage on my 86 Mustang GT. There are some places that are good, yet some have some surface rust. For the epoxy primer, do I need to clean it all to bare metal? Does it matter if there are some spots that have some traces of paint? (the rust will be gone) If its best that its bare - I'll do it. I wanted to bush/roll it on. I read in some older posts that it can roll out decent. Reduce 1:1 to roll/brush? I know.. lots of questions - new to the product. Thanks!