Spray thickness of primer and paint

About one mil, dry film.

Sorry, I just couldn't resist :o).

Seriously, there is no way I could tell you how thick in any kind of meaningful way. Assuming:

1. You are using the correct materials
2. Mixed them in accordance with the manufacturer's recommendations
3. Are using a properly adjusted spray gun intended for the material you are using;

then if you spray it too heavy, you will get runs and if you spray it too light you will fail to get a good, smooth finish. The best way is to practice, practice, practice. Do it on a piece of sheet metal in the vertical position, say 3 or 4 feet square. You'll find out what works and what doesn't. You should never attempt a tractor (or anything else important for that matter) the first time out. You would be asking for disappointment. It's not hard but it requires a certain level of skill and confidence that can only be learned by doing.

Rod