I'm only estimating, but I think more than 90% of my models have been painted with a paint brush, including the clear finishing coat. Some have been a mixture of brush and airbrush, the latter mainly for the clear coat again, and a couple for mottles. It's only since I got my current airbrush, and a compressor, the former about 3 or 4 months ago, that I've started airbrushing more, but even then, it's still a mix of the two. And I always use a paint brush for the individual parts, detail parts and interiors etc.
It still amuses me that everyone, or so it appears, seems to think that an airbrush is a 'must have' tool. OK, I agree, it is a superb tool, and I'm really pleased I finally got a decent , fine line jobby,and especially pleased that I got myself a compressor, but I firmly believe that the 'hairy' brush should be mastered first, even if only to understand how paint works, and how to achieve different effects.