I used a Copper Tekna with 7E7 Cap and 1.3 and 1.4 tip to paint my car. Gun also included a digital pressure gauge. Cost was a little under $400 shipped. The 1.3 is intended for base and 1.4 for clear. You don't need a separate gun for base and clear, just be sure to clean the gun very good as soon as you are done. Since we are not doing this for a living spending longer to clean the gun is no big deal, certainly not worth buying two guns.
I don't recommend trying to paint outdoors. I can't imagine the conditions 40 miles south of me would be that much better. I always had bugs, leaves, trash, pollen, etc blow on anything I attempt to paint outside. Get some 2x4's or PVC pipe and construct a frame. Cover it with automotive grade plastic sheeting. The roll I purchased was 12'x400' and sold for about $30. This sheeting is designed so that paint and over spay sticks to it and does not flake off.
I think part of my success in painting my car in my basement was due to use of this sheeting. Look at post 390 and you can see that I put this stuff down everywhere. Dust is also attracted to this plastic.
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