As a keen painter with less than 2 years experience using my airbrush, I still consider myself an absolute noob when it comes to handling this expensive peice of kit. I’m still searching for the definitive guide to using an airbrush at this scale (15mm) and don’t want to run the risk of ruining my minis by experimenting on them. I read that practice makes perfect but, let’s be honest, that’s boring, boring, boring. Add to this the seemingly inexhaustible technical problems you can experience and it just seems easier to leave the airbrush for basecoating and hesitant attempts at tri-colour camouflage :L.
That’s why I have to give the guys over at FineScale Modeler a big thumbs up for their Easier Air-brushing feature in this March’s edition (UK, Vol. 30, issues 3):

Contained within are 2 really useful pieces on airbrushing entitled Airbrush Maintenance and Problem Solving and Solving Painting Problems. The latter illustrates 8 of the most common airbrushing mistakes and how to fix them:

As a victim of Spiders, Runs and Splattering I found this piece invaluable and it now secures a permanent place above my workbench for reference purposes.
These 2 articles are supported by a video illustrating how to clean your airbrush:
Cleaning your airbrush – FineScale Modeler Magazine.
Well worth the £3.50 cover price.