Necessity is the mother of invention.

[mklotz]

It may look strange but try inflation by a car tire with one of those bycycle pumps and that looks just the nuts. It literally takes forever

I don't think he's trying to inflate the tire. He's simply using the tire as a reservoir tank to even out the pressure fluctuations from the pump so he has a nice constant airflow at the paint gun. The tire serves the same purpose as the capacitor on the output of the rectifier in a direct current power supply.