This was my first experience painting using a paint gun and air compressor. I had practiced on scrap material to make sure that I had the "feel" and that the flow and pattern were properly adjusted. I am using a Cobalt gravity-feed spray gun that I purchased at Lowe's. It has a small plastic reservoir that can be adjusted to remain vertical whether you are spraying parts hanging on a wall, or parts lying on a table. It is easy to clean.
I am using Cortec VpCI-373 (green) primer to prime the internal parts of the aircraft structure. The purpose is to protect against corrosion. This is the primer that is used by Zenith Aircraft Corporation on their S-LSA aircraft and the one that they recommend for their kits. I really like this primer because it is water-based and non-hazardous to the environment. I can spray in my garage and there are no odors and no mask is required. Cortec has shown that it is every bit as effective against corrosion as the common (and hazardous) zinc-chromate primers. The US military uses Cortec VpCI-373 (green). A thin (2.5 mil wet film thickness) coat is all that is required for corrosion protection. Unfortunately, I could not find the primer in less than a 5-gallon pail (about $250). I divided the 5-gallon pail into 6 almost-full one-gallon paint cans (easier to stir with a less-than-full gallon) and sealed it. The Cortec folks said that I could expect a 3+ year shelf life if the cans remained sealed and at room temperature. By the way, Angel Green at Cortec is a great technical resource at Cortec. She even suggested a way to open the 5-gallon pail (it requires a special tool that I don't have).
The priming went well. I found in my practice that it is better to adjust the spray gun for a lower flow of primer, and then make multiple passes until the aluminum is just covered. If the spray gun is dispensing too much primer, it will run. Another nice thing about the VpCI-373 is that it is fast-drying--dry to the touch in about 5 minutes (this on a humid summer day, too
