Sounds like you're using a conventional nozzle setup on the gravity feed gun you have. In that case a 2hp would be plenty for painting small things like fairings for bikes and such. Keep in mind what hairbag said earlier in this thread. It's all about CFM. With the Conventional tip you will be using MUCH less CFM than a HVLP model gun (HVLP = High Volume Low Pressure). HVLP guns use a high volume of air at low pressure to atomize the paint as opposed to conventional models that use just use high pressure, this helps avoid bounce back and overspray. Anyway to make a long explanation short... your gun should work fine with at 2 hp compressor. As for gallons the compressor holds... The tank is just a buffer for your compressor. It fills the tank to max pressure then shuts off. This insures that you get steady pressure all the time. As for using the air in the tank while the compressor is going, that's fine also. So long as you aren't using the air up faster than the compressor can fill the tank back up. I usually try to keep my compressor from running for more than 2 minutes at a time. Otherwise it gets hot and could seize up on you. I hope this makes some sense to you.
