Any recommended sources of information?:
Kalmbach publishes many books on model finishes and detailing. Look in a copy of "Fine Scale Modeler" magazine (also published by Kalmbach) for titles. There are several videos available as well.
Airbrushing:
Thinning the paint and selecting air pressure to suit the job are the important parts to using an airbrush. Remember that the instructions are pretty general. The closer to the surface you spray, the less volume you want from the airbrush. Check a scrap piece of plastic first to adjust thinning ration and volume. Them move on to the model. DON'T use paper, as it will absorb excess paint before showing runs.
Washes:
I have heard of giving models a wash to bring out surface details. How do you go about this?
You need to wash and drybrush to bring out surface details. Washing, and I use artists oils to tint mineral spirits, emphasises shadow detail. Drybrushing emphasises surface detail.
Washes, therefore, are usually dark (but not necessarily black), drybrushes are generally the surface colour with progressively more white mixed in. Actually, I don't like white, it looks too stark. I prefer very light grey.
Washes - Using Oil Paints:
A warning to those using oil washes over water based paints. Beware.. Paints like Tamiya may be affected by Turpentine. Make sure you spray multiple coats of a glosscoat like Microscale and let it dry thoroughly. A thin light coat might now be a sufficient 'barrier'.