Alkyd enamel was THE high tech factory paint from the 1930's till the 1960's, as far as I can find.
I finished my truck last summer, almost a year and it still polishes up after a wash free Canuck winter, daily use, scrap metal runs and several other indignities. I'm pleased and impressed with the results and anyone who doesn't like it, doesn't need to paint with it. No one is holding a gun to their head.
I like the money it let me put into mechanical work and the fact that it no longer looks like a chameleon exploded trying to hide in a box of crayons.
I'm about to start the second round using the same method, having bought a new box, hood, fenders and doors. Hmmmmmmm...... sounds like I should just jack up the emblems and drive another truck under them, almost a full rebuild
As for cheap, we should all get together and start a company making copper wire by stretching pennies