I would agree with the epoxy. I never use less than 3 medium coats and apply it right after sanding/cleaning. Are the $300 epoxy systems better than the $70 epoxys??? Takes more experience than I have to really answer that but I have found that some of the lower priced epoxies are tough as nails but can sometimes be a bear to feather if needed. Sand the metal with 180 grit DA and clean good. Preparation is as important as the paint used.