Guys I have been reading this post, but I didn't feel that my input would be helpfull. It may still not be, but I am going to give it anyway.

I painted my ragged old Ford 900 farm tractor 4 years ago with the red Rustoleum paint that has been used in this discussion. I did not thin it, and I sprayed it with a very very poor quality conventinal suction paint gun. This was literally an attempt to make the tractor look a little better since I had just rebuilt the engine and replaced the clutch. I was so happy with the results, that I took the time to get the correct contrasting grey color and painted the tractor the proper way. The stupid thing still looks good when I take the time to pressure wash it clean(ish). Now this is a work horse, not a show tractor. The paint has held up far better than anyone expected. It is worn off on the pedals and running boards. It is scratched in places where limbs and branches have hit it. But it still looks respectable. I had enough left over from the gallon I bought to put a quick coat on a junk work truck (that I acutally bought as a parts truck for my project truck). I regularly drive this truck through the woods, and don't stop for saplings or blackberry thickets. It is also scratched, but the paint still sticks. I did not do a good prep job. I didn't even wash it. I gave it a quick scrub with a scothbrite pad, blew the dust off with the air hose, and sprayed the paint at it. The paint stuck very well. If I had taken at least some time to do a halfway good job, it would have been very presentable wihtout sanding at all. The two front fenders and driver's door on this truck were stripped to bare steel to be used on my project truck. They had too much filler, too many very bad dents, and too many slide hammer holes for me to bother with for my good truck, so I slapped them on the junker. They recieved no primer, and have not rusted in three years. The paint works. If you care to take the time it could make for a good looking driver. I doubt it can get good enough for a show car, but for a daily driver it would be cheap and easy to use.