There is simply no way I'd want to paint a model that large with any sort of air brush.

For what you're doing and if you'll be doing enough of it then a nice option that is sized to work well on our models would be this gun;

http://www.harborfreight.com/air-too...gun-66871.html

And of course you'll need a compressor that supplies at least 5 CFM at 40 PSI. More is better. And if you're working in humid conditions you'll want a water separator and inline drier. Otherwise you'll end up working with water based paint even if you didn't plan on it....