Primer what to use

I would avoid doing bodywork over epoxy. It's the new "craze" but in my opinion it costs more, takes longer, and makes more work for you with no change in end results. Epoxy sands like crap and all it will do is create the above problems. I also have used NCP 270-271 PPG primer for years and its a great primer. You can put it directly on bare metal and is a great corrosion resistant primer as well as having excellent filling properties.