Don't clean the bare metal with Lacquer thinner. Use something like PPG DX 440. I also have had better luck with etch primer than epoxy on bare cast iron. Aluminum can use either. I use regular single stage urethane. The chrsler spray isn't bad but its not as good against fuel,brake clean,etc. The urethane isn't fazed by either. This is a 5 year old job we did.
Doug