Primer

Everyone has their reciepe. Mine. Filler over epoxy primed metal NOT bare metal. Yes that worked for many decades but there is a better way.. Epoxy primer over cured filler. High build urethane primer. (Consider polyester primer is areas if needed.) Block. Block some more. Check for any flaws anywhere. Guide coat if you need and block that. Is it perfect? SEAL it with a sealer as in reduced epoxy primer, then Topcoat in appropriate time window..