JF4 and DDG....I dont know WHAT I could say to try to steer you away from using water based paint products along with urethane-based clear. There are SOOO many things that are just sick and wrong about that, that it make me feel (in the immortal words of Redd Sanford) 'like the BIG ONE'S coming!'!!
I have used Createx's paints for airbrushing T-shirts. And I have used their Auto-air for spraying testing pieces to see how it would work. IMHO, Createx Sucks! It costs just a hair more per 2-oz container than what I am charged for touch-up size containers of PPG or Doupont paint, and it voids the warrantee of your PPG or Doupont Clearcoat when you spray it over Createx. Sure, I've seen the jet-ski and helmets that have been sprayed with createx autoair, but if I were spraying my own car (which I have), I would stick to something that has historically shown the best turn-out for the $$...I mean, think about it...IF there were a Water-based paint that gave a remotely similar turnout to basecoat/clearcoat paints, wouldn't places like Earl-Shives and Maaco be using it? And would custom painters be using it too? I mean, its' easier to clean, you don't need to spend money on reducer, or parts cleaners...it's safer to store...
But the bottom line is, Createx should stick to making T-shirt paints...the Auto-air paint has been out for a while, and it Still Sucks.
The 'hopper
*This is my opinion, and it's only MY opinion. Had this opinion been a truth or General-Knowledge of the Public, I would be making money copyrighting and selling it in a book somewhere. This is ONLY my opinion.*