Umm, I wouldn't want him to shoot whatever! Waterbase color is fine but the clear is what protects it. $4500 is a good price for bodywork and paint but don't let him skimp on the quality of materials. A good clear is gonna cost ya $300-$450 a gallon.
PPG Concept or Global, DuPont Chroma-premier are the leading clearcoats. There are others but these are my choices. Be sure you know for your piece of mind.
I'm sure knowing how you are with other things you will make sure he does the right thing. Can't wait to see how it turns out!!