Actually, if you do a lot of airbrushing, you'll find that you end up with multiple guns for different reasons anyway. My first was a Badger single-action which I still have. Those are actually good for covering large areas. Just preset the paintflow and blast away. I have a Paasche dual-action that I also use for larger coverage because my Iwata is better for small patches and shading. So if you do a lot, you'll ultimately just end up with brushes for different jobs.
