for what it is worth, I find the "spray until no color comes out" does not mean the airbrush is necessarily cleaned, unless you are just trying to clear out the old color before starting with a new one

the advice given earlier of taking off the nozzle, and cleaning the needle is a good one

often I will not be spraying color, but when I take it apart, their is dried/semi-dried paint on parts and cleaning that off will help prevent future clogging

I typically use either Tamiya, or Vallejo model air, and I find taking the airbrush nozzle off and loosening the needle so I can push it forward and backward while running some water through it from the tap is the best way to clean it out. If I do not do this, often the next time I try using the airbrush, the needle will be stuck in place

every so often a full disassembly and soaking the parts in alcohol will do wonders for it