The can says it doesnt need a primer. I applied it to a stripped and wire brushed raw metal frame. Gave several coats (rushed it, should have done many very thin coats) and it came out great IMO. I used the rustoleum version.
Nice and glossy. Needs to cure for quite a while as with any rattle can. No baking here and it's been colder winter weather.
Next I'll try some high temp engine enamel. It came out beautiful and exceptionally durable on my valve cover (unbaked).