I recently did this to my 1987 34' Avion (which is shaped pretty much exactly like the new Airstreams....or rather they are shaped like it

) because in 95 degree sunshine the a/c was getting over powered and a guy with a 34 foot 'stream told me he'd painted his roof white for the same reason and he saw a 10 degree internal temperature drop.
You do have to etch aluminum for the paint to stick to it well.
Through a friend of a friend that works at US Air I was able to get some self etching aluminum primer that they use on their airliners. I also got some metal prep cleaner / etcher called "Metal Prep 79" or something very similar. You can get that from Aircraft Spruce and Specialty or places like that. You soap and water wash it really good first. Then you hit it with the metal prep 79. Roll it on heavy, let it sit 10 minutes, then rinse it off thoroughly. After it dries, I put on the self etching primer (get a good mask, the VOC's in it are nasty) with a roller. After that, you could use about any good oil based paint. I had some US Air gloss white, but the VOC's gave me a headache from the primer (and I was outside doing this with a mask on....apparently not a good enough mask) so I used gloss white Rustoleum. Like I say, once you get the primer on, the hard part is done. It turned out really nice. We had an 80 degree day the other week and the coach sat out in the sun closed up all day. About 4:00pm I went inside and it was very much cooler than it would have been before. There is something to the gloss white reflective paint.
I do still plan to replace my 21 year old 13,500 btu Coleman with a new 15,000 btu model. I'm hoping that the two combined will fix the problem. If not, then it's a new 60amp intelipower and I rewire the coach and put a second a/c in the bedroom.
Cheers,