I use it for all my stuff, rust primer protector works great and is half the price of the por-15 stuff. And as far as a car job though, you can cut the paint down and run it through a paint gun and it will still look good.
i used rustoleum paint i sprayed a 89 ranger with awhile back. the directions said how to cut it down and i used a spray gun. it turned out really good but i didn't get a gloss color. kinda wish i did.