You are correct. Bare metal is best to be coated with Epoxy primer and is typically the very first step after stripping a car. I don’t like how I went though to metal in these spots. When I got the car some of the body work had already been started and most of the panels were new and had the black electronically coated primer on them. I chose to use Urekem 2K Polyurethane High Build primer as it’s rated for DTM if it’s been sanded with P220-400 paper. It’s also good for various other surfaces such as paint and filler. I used this since I was coating over basically everything. Thanks for the question.