I do a lot of airbrushing myself. I've found the Iwata HP-C to be more than you need to do anything Wargaming related. Its probably scale model grade. If you're going a large amount of airbrushing or have a limited color pallet you might think about the HP-CS which is a bottom feed siphon airbrush, you can effectively mix up large batches of paint and do significant portions of you army at the same time. The HP-CS is great for vehicles for this reason. The Badger 105 is another brush worth looking at. Its on par with the Iwata, the parts are cheaper and easily obtained online.

Ryan