One gallon to do the whole car at least, get a water trap for the hose and gun, regulator, 60 gallon compressor, find some way to do it in the garage if you can and put plastic up with fans. If you get some trash in the clear then you can just wet sand it and have minimal trash. Follow the directions on the can. Noone can really tell you the reducer and such to use because the weather changes all over the place. Ask the local paint supplier and see what they say.