How thick do you recon they get the PU topcoat? I know the PPG Concept we've use recommends two wet coats of 3 mils each for a total of 6 (this is for their standard auto applications). This then dries to a very thin (1-1.5 mils). We were able to get thicker coats for maybe 8-9 mil wet which seemed to give us (barely) enough material to color sand (wet sand). The automotive guy who did the Urethane paint couldn't understand why in the world we'd want to mess up his perfectly good spray job (with only very minor orange peel) by sanding!

As a sidebar... now that I've messed with this stuff, I can't help but look carefully at every car I see in the parking lot. I was looking at a Mercedes GLK the other day which had what glider guys would consider "bad" orange peel on a factory finish. On the other hand, from a work perspective, it's much more efficient to just "spray and forget it".

p3