[Setec Astronomy]

You can still work in quadrants with the foam gun, or even smaller areas--if you can't keep from blasting the whole car at once you must have some hellacious water pressure--try throttling down your faucet a little. As Timmah said, you can rinse with the foam gun, either by rotating the orifice rod so you're not siphoning, or disconnecting the cup portion from the trigger handle with the quick-disconnect built into the gun. Or you can put quick-disconnects on your hose. I think one of the real values of the foam gun is on the sides of the car, where you can actually get some soap on the dirt before you wipe it, as opposed to trying to slosh it on with a mitt and mostly wiping dry. I think that's mostly why the foam gun seems to use more soap--you are actually using some on the sides of the car.

OTOH, to each his own, there certainly is some more rigamarole to using the gun.