2-3 coats of Pettit Rust-Lok will stop it from rusting. Just sand off most of the rust and apply. You can paint over rust with it but who wants to do that? It's a one part paint that can be brushed or sprayed so application is simple. Once it is fully cured, it will have to be roughed up before being top coated, but that is true of most modern primers that actually seal out water. The paint is also almost impervious to solvents, even MEK doesn't take it off once dry.