I have tried various water-based products over the past 15 years or so (woodworking and modeling) and to be honest, I can't even get a good start with them. Plastic model acrylic tends to clog up the airbrush due, even if you do get it out of the gun and it won't flow out on plastic, no matter what you clean it with. Woodworking water-based polyurethane also won't flow out, sprays poorly, and raises the grain drastically on every coat. I have tried every suggestion from the experts, and still, I end up trying to strip it, with great difficulty, and just grabbing a can of Deft spray lacquer, half a day, done.
I assume it is some technique problem, but putting water on wood seems like it is always going to raise the grain, and I expect water to bead up on plastic, so my results seem pretty intrinsic to the medium.
Brett