Here's what I know...
the spitting is possibly (probably) water vapor from the air compressor. You should get a moisture trap to put in the line, just off the air comp. This really fixed me up. I don't see any moisture in the trap, but I'm not getting the spiting anymore. And when I empty a tank, the bottom nipple spits out water, so i now it is in there!
Acrylics - I have used them and HATE them! But my wife and everyone else in the universe has great luck, so don't go by me. You are right about the special thinner, you should never use water, the thinner is excellent. I'm told that the outrageously priced thinner (something like Euro 15) for 250ml is only isopropyl alcohol and some soapy additive. I have used straight iso alcohol (methylated spirits) from the hardware store with good result. That's only about Euro 3 for a liter!
I was using Tamiya paint, I love their stuff, anything they make. The paint quality wasn't ever an issue, it's just that I like the "bit" of enamel/solvent stuff. But I'm going acrylic for my Graf Zeppelin, I think it will be faster and easier clean and there's nothing too special about the paint job.