Re: air compressor question
You should be using a regulator/dryer setup on any spray gun so as long as the tank is big enough, you should be alright. Running full pressure to spray is a bad idea anyway, so the regulator will slow air use enough to work. A small gun like you plan to use should be fine although you will probably have to stop occasionally to allow the compressor to catch up.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.