I going to guess you mean an inexpensive badger airbrush?.....cause I don't think the expensive ones have glass bottle feeds.
I clean mine by running hot dish water through it or wiping it with a soapy rag. It's a really forgiving easy to clean brush! I have submerged my pen in dish water to clean around the inside rim and never had any problems. Because the chocolate doesn't feed through the needle/air spray the pen really doesn't need deep cleaning or special cleaners. You can just plain hot water with-out dish soap too.
Keep in mind these are cheap airbrushes so they don't last forever. But here's a good tip (I've learned the hard way) in time when you brush breaks KEEP it! So when the next brush breaks you can use the old one for parts. Because you can't buy replacement parts for the cheaper model.