It's been a while since I've done much airbrush work (used to do 1/72 airplanes), but the fuzziness of the edge with the template method varies directly with the distance between the templace and the work. If you put the template right up to the model, fuzziness should be minimized--and if you're careful with the angle of the airbrush, you might be able to eliminate it by shooting from "outside" the edge of the template you're using as a mask (brush tip outside the "hole," shooting across the edge and back into the hole). I wish I could sketch it for you.
Best of luck,
Ken