Hi Dave and welcome to the forum.
I'm afraid that airliners are not my thing so I'm not much help there but I know a few members here who will be glad to help.
As for airbrushes it is all really driven by price. I would start off with something cheaper, without getting into the toy area, and if you take to it go for something more expensive. The experts use the double acting brushes, which are undoubtedly more controllable, but you probably need to gain a bit of experience on something simpler first.
I would think carefully about how you are going to drive it as well. Gas canisters cool with use and affect the brush pressure, which is very frustrating and makes life difficult. Equally a compressor that doesn't have a reservoir is not a good way to learn so I would look for a good quality compressor that will drive many air brushes for years to come, fitted with a decent reservoir. I actually thank that is more important than the brush to start with because pressure challenges are guarranteed to put you off right from the start.
I have a Clarke Shhh 2/9 model, which came in at about 250.00, but it will last a lifetime, will power airbrushes as well as other workshop equipment and is very quiet in operation. More importantly your pressure will never vary.
Have a look here:
Clarke - Clarke Super Quiet Air Compressor - Shhh 2/9 - Ultra Quiet Air Compressors - Machine Mart
As for the airbrush itself, start with a single acting one that is easy to use and dismantle. Badger do good solid beginners brushes that will do you good service to learn the trade then you could move up to whatever you want, limited only by your wallet!!
Something like this would make a good first brush:
Badger Precision Airbrush Set 2003 - £50.99
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