Thanks all..
The dust on the Mathilda is a mixture of brown, yellow and white pastels covering up some tamiya dark earth which started to spatter after my can-o-air(tm) expired. so I though, what the heck. I had already botched one paintjob (which was, ofcourse, better) on it. For some reason (not enough pressure?) the paint didn't mist very when I tried to do a dust coat. Probably just as well, I suppose.
To be honest, the Jagdpanzer is my favorite of the two, which isn't quite fair towards the Mathilda, though I could've done the ambush spots a bit better (finer, more frequent).
I'm very happy with my new airbrush. After a moment to get used to it I was painting lines I'd worry about doing with a normal brush. Well worth the extra time to clean it. It does, however chew vast amounts of air compared to ye olde oxen wagon of a single action I have (and use for large area painting).