I've heard of a guy (can't remember his name) who does hand-painting only. He ironically won an airbrush at the last IPMS.

If I could give you any advice (and by no means am I great at this):

-Know your paint, know what thinners to use, know what works well for hand-brushing (Vallejo for example)...and what doesn't (Tamiya)

-Wash and prime the model (oils from your hands mess up hand-brushing more than airbrushing in my opinion)

-Use a fluid retarder or slo-dry medium to slow the drying time

-And like Q said, LAYERS. It took me a long time to realize this, but layering light translucent coats really helps.

I often add a drop or so of Future to most acrylics I use for hand-brushing since it thins it down and slows the dry time a bit. This would make a matte coat a little less matte...but that might not be so bad.