Sanding grits on bare metal before primer and after

[theastronaut]

80 grit is usually recommended for bare metal before epoxy primer. I like 60 grit since it stays sharp a little longer.

For filler work you should start blocking it with 80 grit to level the filler, then apply guide coat and block with 180 until all of the 80 grit scratches are gone. Primer over 80 grit scratches will cause problems later when the primer shrinks.

Seal the bodywork with a couple coats of epoxy, then shoot a few coats of high build primer and block it again, start with 120 to get it straight. If you go through anywhere you can spot those areas in. Finish with 320, then 500 using guide coat in between.