There are two sources of air to power a spray gun: a compressor and a turbine. Compressors are much less irritating; simply plug them in or turn them on and leave them. The motor will come on only when the amount of air in the tank gets low (after you have been using the spray gun for a while), so there’s no unnecessary noise in your shop.
A turbine, on the other hand, runs continuously whether you’re spraying or not. It makes a lot of noise, and air is being expelled continuously, either from the gun or from the turbine unit, which may kick up dust. You can walk over and turn off the turbine, of course, between spraying steps, but doing this can also be irritating, especially if you locate the turbine a little distance away to reduce the dust landing on your work.
So here’s an easy solution. Plug the turbine into a remote control you can buy from most electronics suppliers, and turn the turbine on and off when you aren’t using it from the remote in your pocket or on a chain hanging from your belt.