I agree with Darrin,
Epoxy is what I have use the past 34 years with out any problems. My brother worked for PPG for years and the original DP epoxy was fantastic.. then they removed the lead from the epoxy..now it is called PDLF (lead free)..I don't like it and I talked to the Rep about this... he told me on a brake that he couldn't tell me this in the class..but anyway..he told me not to use the DPLF..he told me to use the Omni Epoxy, it was closer to the original epoxy. So I have been using it for years..and I have had no problems.
You have a 3 day window with it to apply body filler, primers or top coat with out sanding.