Crossing posts!
Carpediem, nice job! An airbrush is far from essential, and is really a luxury. Some extremely good, if not superb, jobs can be accomplished with the old 'hairy stick', and in fact, I still use a paint brush probably 50% of the time. I only really bought my first airbrush for finishes such a mottles, and it's only since buying a newer 'brush recently that I've started using it more.
I'm often asked about painting techniques and how to achieve various finishes etc, and a piece of advice I'm never afraid to offer is to use a paintbrush, in various styles and sizes, and get to know how paint behaves and works, and just what can, and can not, be achieved using various techniques, thinning ratios etc. My personal opinion is that too many modellers consider that an airbrush is a 'must have', and that it will dramatically improve their modelling skills. To an extent, this is similar to a brand new driver thinking that a luxury car, a Ferrari for instance, will make them a better driver!
Whilst there is no doubt that an airbrush is a very useful tool, and can, with practice, provide results perhaps difficult to achieve with a paint brush, it is just that - another tool in the box, and by no means absoulutely essential, with the possible exception of some complex shading or mottle finishes found, for instance, on some Luftwaffe aircraft.