Jeff just got the tech sheet on DP epoxy primer. If you are using DP-LF from PPG then you can sand the bare metal with 180 grit sand paper. You have to use a DF body filler "bondo" on top of that because regular bondo will not hold to the DP-LF.
Sorry I am not much help I haven't used epoxy primer since the good old DP 40 days. That was good stuff but bad for the environment and on the body I guess.[/QUOT
Remember if you have bare metal and it is not painted over real soon you should re sand it lightly to make sure no rust is there even if you don't see any signs of rust prior to priming.
Just my 2 cents.