First of all, I'll mention the painting and airbrushing forum. This forum is often overlooked because it is at the far bottom of the FSM forums. However, it is full of really good advise and I urge you to give it a try.
That being said, there are/have been some recent threads about airbrushing overspray and need for a spray booth when airbrushing. I agree with Gary. While I have a spray booth I only use it for rattle cans. I do my airbrushing right at my building bench, with no booth there. I ordinarily get so little overspray that it is not a problem. I do have to be careful to avoid having another model or another subassembly directly on the bench behind where I spray, but I usually notice that immediately.