I was looking for a way to speed up my painting and decided to try airbrushing contrast. As you can see, the result is fairly decent considering the time spent. What you see here is a zenithal priming (black, grey then white) followed by airbrushed skeleton horde (with about 20% thinner in it).
Looks great! I just discovered this too a couple weeks ago (albeit using Army Painter speed paints). I always struggled with brush stroke lines with speed pains but the air brush made great work.