Air brush is the only way to go. To economically get started, a couple of suggestions:
1. Go to Wal-mart and pick up a Cambell-Hausfeld air compression. The model I have has a small air tank and cost around $90.00.
2. Find Dixie Art on the internet and get yourself a Badger 360 airbrush. They ship for free, you avoid sales tax, and their prices are about 1/2 usual retail (I recently picked up the new 20/200 detail brush for $40.00 delivered). I used a pasche and one of the new aztec brushes, the 360 puts them to shame with operation and ease of cleaning, especially if you use acrylic paint. I thought the aztec was the best until I tried the 360, after using it I gave my aztect away.
3. Get rubber surgical gloves and a good 3-M air mask, not just a dust mask. Paint and its fumes can be very harmful, even if it only is on your skin.
4. Paint booth. I know they are expensive, but it's hard to put a price on healthly lungs, as you only get one set.
5. Don't be afraid to screw up a model and practice, practice, practice. I keep my older models around as guinne pigs for camo scheme practice.
6. Have fun with it. I have the tendency to be so focused on the end result and perfection of the painting job that I forget to have fun painting. Relax and do your best. You'll get better and your work will improve.
For around $170.00 you'll get a good compressor and excellent airbrush. Also, I would recommend to you use acrylic paint. I washes up in water, as clean up is the big head ache for me, and is much less toxic than enamel paint.
I am far from an expert, probably alot closer to you in skill level than not. If you get the 360 and need any advise, send me a message.
rrennick2000@yahoo.com