Guys, I want to paint my 69 convertible in my own garage. I've been told that using a 20 gallon air compressor will work with a lot of time and patience. I've got a good idea of how to make it happen but one can never get enough advice. That being said, please advise!!!!
It isn't the size of the tank but the flow rate at a set defined pressure that your paint gun needs. For some strange reason manufactures of air compressors only put their larger one or two stage single or dual piston compressors on top of their larger tanks (a flat pancake air compressor for doing roofing is an exception to this rule). You generally need a 33 to 40 gallon tank with a seven horse or larger air compressor to get enough flow to paint without striping or having the paint run (because you can get a wide enough fan without a lot of over-spray).
Though as you say if you are touching up a mirror or painting a motorcycle gas tank you might get by with a twenty gallon tank air compressor kit.