A while back there was a thread about painting a car with Rust-oleum enamel using a roller....thinning it and using about 17 coats...I think it took about 17 weeks to dry as well...lol. I painted the top of my van with Rust-oleum enamel...its peeling already...I really didn't prep it that well though. It seems like you are taking time with your prep which is probably most important. I think Rust-olem is a good product, I use rattle cans for everything all the time.