Zero rust and Rustoleum are alkyd enamels. You can also add a UV protectant to them, as well as a catalyst to make it harden faster.
Question, Truckrolet, what kind of catalyst can be added to rustoleum oil based enamel?
25 or so years ago I used to mix industrial enamels with DuPont gloss hardener, not sure if that is the correct term. If I remember right the paint was an alkyd enamel. It worked great. Good gloss and very hard.