Good advice overall. Actually, this is a must read for anybody starting out.
Couple of things:
You don't need to buy a "milk frother" to stir your paint. You can just buy a paint mixer. It's also cheap -
http://amzn.to/Hmlm5t
I solved most of my issues with airbrushing when I moved from thinning my paint with water/alcohol/Windex to just using Liquitex Airbrush Medium. It pretty much also solves the consistency problem too. You can't overthin your paint since the thinnest it can get it still a good thickness. Transparency is another issue, though.
http://amzn.to/1aAdhnx