65 Chevy guy, you are sure going about this the hard way.
Don't put the Dupli-color Primer Surfacer on the bare metal. It's a High fill primer.
Sand the metal with 320 grit with a DA. This will clean it and prepare it for top coating.
Spray 2 coats of Epoxy Primer/sealer on the bare metal. You can do any body work right on top of this primer/sealer. If you aren't doing any bodywork, then you can apply your top coat on the Epoxy.
I would Coat it with expoxy, then two or 3 coats of 2K high fill primer, block sand to get my surface nice and flat (smooth), one more coat of epoxy primer/sealer and then top coat it with color.
I would be careful with Dupli-color, most of their stuff is Lacquer.
Frank
