For paint busting I use an air buffer with a thick flexible pad and 40 grit hog paper. 36 grit is to aggressive.
Once paint has bee stripped to bare metal, go over it with 80 grit on a DA. This will give you a good tooth for
epoxy primer and then catalyzed primer over that. As long as no old paint remains this is an effective method.
Existing old paint can suck up primer and shrink. A bare metal surface will not shrink paint materials
