You can offset length of the air line with larger size. It depends on your paint gun CFM/pressure demand. You could also pipe directly to the compressor and put the regulator at the end of your pipe where you connect your final hose and paint gun. Don't try to run 3/8" ID hose at the lower pressure, because you'll likely run out of air. As a WAG, I'd say you could probably use a 3/4" pipe at tank pressure.
If you can tell us how far you need to run, and what your gun demands, I could probably give you a better estimate of size needed.
