I redid a quarter panel because I broke the "7 day rule". Sanded right down to metal, then put 3 coats of epoxy primer. After 48 hours, I added filler and sanded it until it was near perfect which exposed some of the bare metal once again. Should I be putting another couple coats of epoxy before going any further ? I know it will need some metal glaze here and there. Or can I get away with one coat ? I seem to be going through a lot of epoxy primer only to sand most of it off when I do filler work.