Bare steel needs to be coated with either an etching primer or a direct-to-metal urethane or epoxy primer. We chose Eastwood’s 4:1 urethane primer. When 4:1 is mixed with activator, it can be used as a high-build filler primer. But you can also thin it by mixing it with a reducer and using it as a primer/sealer. We chose the latter and sprayed the whole car with one coat using our DeVilbiss Starting Line spray gun fitted with a 1.8 fluid tip.