****o WildDuke, "...difficult to spray", no, different...yes. Instead of having one "base" color you now have two, so-to-speak. So as long as you have no problems spraying a two stage system you should have no trouble with a three stage system. The difficulty comes in trying to actually match the color of the rest of the car. You didn't say in your post but if you're painting the entire vehicle(s) then this kind of eliminates the problem. Painting the entire vehicle still doesn't guarantee that one side of the car will truly match the other but the differences in the pearl will be so gradual that no one should be able to tell. Since we're not robots at the factory things like the speed we move our arm, the distance we hold the gun from the panel etc., all play a part in how well the pearl will lay down and match.
Good luck.