water, and i have recently discovered some cleaning stuff froma pressurized can called IPA, bassically high alcohol cleaning fluid, works like a dream, just watch for over spray and don't get it near the latex
I use ammonia. that also thins latex pretty well and you cant tell because it has that smell. the latex is a water and ammonia base. heres my procedure ( most of it came from badger instructions)
1 spray until there is no color left.
2 fill jar with ( in this case ammonia) and spray all different sizes until no color comes out at all.
3 take out jar and turn airbrush up side down and spray.
4 Back flow ( put bottle back in and press a cloth or paper towel firmly up against the end of the airbrush. make sure that the needle is not in the way so it does not get damaged. spray and what should happen is the bottle should bubble. what is happening is you are causing pressure to build up in the chamber which is causing the fluid to go backwards and into the wierd areas inside your airbrush that would not be reached as well if you are just spraying a cleaner through ***make sure you do not do this in an open color cup or it will spray fluid every where***)
after that i dissemble the the front and clean the need softly with a sponge and i use a tooth pick or sewing need to clean the dried latex (if any) inside the needle housing.
Make sure you have ventilation or you are spraying the ammonia into a cloth or else you could be breathing in some intense fumes. It might also be a good idea to water down the pure ammonia.