You want something that is specifically called Rust Paint, there's a few different companies that make it like Rust Check, Tremclad, Rustoleum, etc. This is the one that I used:
Looks like a nice job, well done! I'm not quite so ambitious, I just spray Fluid Film aerosol on any rust that I see developing to prevent further deterioration.
"Even the first coat of rust-proofing has been reformulated so that it is one-hundredth as thick as — and thereby cheaper than — the coating on other cars."