that's very good to know.

Would either paint give me the half-gloss look I'm going for? Maybe still add flattener??

Also I'd really like to use epoxy primer on bare metal then scuff sand, skim with bondo (doing lots of good body work just need to clean up welds), then start with the products you recommend?

Please tell me more! I'd love to use a single stage if it would give adequate protection.