Years back I worked Saturdays at a friends dads used car lot . Spent a lot of the time patching up rusty $500 trucks trying to make them $1000 trucks. Our paint of choice was oil based implement enamel that we could buy at the time for around $10 a gallon. It worked well , layed out somewhat smooth and once it dried after a few days had a durable finish. Later we found we could use an automotive paint hardener and cut the dry time to overnight. Used to get a good laugh when I would see one of them years later still rolling down the road with my $25 paint job. That cheap paint really held up , The only thing I noticed was that you would see some chalking on the hood and roof because it doesnt offer much UV protection. Nice thing was the range of colors was nearly unlimited . IH red , John Deere green, Case orange and so on . Every once in a while we would just mix up the partial cans to come up with an "unusual " color " .