I've been reading this thread with interest and I'd like to offer an 'outside the box' observation. I believe there is a much easier and less expensive way to paint an airplane. But, I know I will have tomatoes thrown at me...
I've painted two airplanes. Both were tube-and-fabric but both had a lot of aluminum and fiberglass parts.
No one here is interested in painting the fabric so I'll leave that part out. But for the aluminum, it was simple and cheap. I scuffed the parts (alum gear fairings, wings struts, trim tabs, canopy bow frame, etc...) with a scotch bright pad, cleaned it off with cheapo alcohol, sprayed it with two-part epoxy primer, and then top coated it with Superflite paint. Done! I didn't use or need any aluma-whatever or any other expensive and dangerous chemical cocktail to 'prep' parts.
I used a Citation HVLP and the parts came out perfect. No orange peel and no runs. For as long as I had the airplanes the painted parts were tough as nails. No paint peeled and no paint chipped. In fact, the paint was very difficult to scratch.
If I recall, a gallon of epoxy primer was around $60. I read somewhere in this thread a guy paid $1,100 for 1.5 gallons of PPG?!?!
For fiberglass parts, there's no way you're going to get all the pin holes out before you prime it. Fill what you can...shoot a coat of epoxy primer...and then fill the holes. I used a cheap red filler that comes in a little tube from Autozone. My wheel pants and cowl had ZERO pin holes. I'm either really awesome or my bone-simple technique just works well!
It's my observation that the RV folks seem to make things as complicated as can possibly be! I can surmise why, but I won't post that here.
Anyway, it's just something to think about. I really don't think painting has to be as difficult as people make it.
I've currently packed my RV-7 away to build a Zenith Cruzer on amphib floats and so far my plan is to paint the entire airplane with two-part epoxy primer and Superflite paint. I think that's the least expensive way to go that will still provide a fantastic finish.
Oh, and the other thing I wanted to mention if it concerns you, the primer and paint went on extremely thin and smooth! So don't think that it's going to add more weight to the plane than PPG or anything else. I was really impressed with how thin and shiny it came out.
Primer on my S-6S wheelpants as described above...http://www.ransclan.com/30jun10.htm
Paint on my S-6S wheelpants as described above...http://www.ransclan.com/8jul10.htm
Finished Wheel Pants...http://www.ransclan.com/1aug10.htm
Paint on Cowl...http://www.ransclan.com/27sep10.htm
Finished Cowl (look how shiny it is!)...http://www.ransclan.com/Log%20Pages/6oct10.htm