"Rust, whats not to love?"
It depends on they type of paint you use.
Thinner works great if you are using solvent based paints.
There are diffrent brands of 'airbrush cleaner' as well.
Personally I use polly scale paints. I will run a bit of distilled water through the gun then hand clean with airbrush cleaner. As you probablly learned in A/B class, clean your guns after each session.