I reckon get handy with a cheap airbrush set and a bit of practice and it will be bonza. There are alot of videos around on "how to" use airbrushing successfully.
Practice makes perfect. Thats what i am going to do with a recently acquired set myself. If u had to pay someone else, it would be too dam $$ expensive so it looks like a few of us are going to have to become self taught.lol
Bunnings can also colour match with their computer paint analyzing software which will be a big help. Definately worth giving it a go. 
I would not recommend a cheap airbrush (depends what you mean by "cheap")
. I brought a $22 set from bunnings and it is crap. I ended up taking advice from Gavin (Retropin) and bought a dual action set off eBay worth over $180 for $84 delivered with an air flow adjuster.
I've been teaching myself with some help from Gavin and Timbo and the results depend on the quality of the airbrush and the paints. It's great fun as well
