Use Rustoleum oil based paint you get from Lowes. To make olive drab, mix one quart of rusty metal primer with one quart of hunter green. I use it for everything, wood or metal. Blinds, feeders, shooting benches etc.
Rusty Metal PrimerHunter GreenI thin it and spray it on with this HVLP sprayer from Northern tool, but you can brush or roll too.
HVLP Sprayer