Yeah, get the water out. You can get a little "last chance" filter for your gun. Don't sweat little errors, most can be wet-sanded out (unless you are shooting metallic). Wipe the car down with some kind of cleaning agent or lacquer thinner. Then get a couple of tack cloths and wipe the whole car down for dust and particles. Follow the directions on your paint. Keep your gun clean. Spray some test patterns to test your gun setup before you shoot your car.
Spray the inside of the sail panels first or early. You know, right where the engine lid and rear window is? Otherwise you will have to lean over your fresh paint to get to them.
I wetted the floor and the walls with a hose as well. DON'T DO THE CEILING THOUGH!
Most of all HAVE FUN!!! Its a blast to shoot your own car.
