There's a cleaning agent called perfect cleane. It's from AK. It's the best thing I've found to help clean your airbrush. Having a clean airbrush is important. This stuff is just great. I've airbrushed some parts and just put a few drops of perfect cleaner in and spray it though and you can come back and pick it up and start back without a deep clean of the airbrush. I know that this is not what you've asked but I've only been airbrushing for about a year. I've had the same effect also. especially if I'm swapping paint without a good clean. I've used alcohol and x-20a thinner spraying tamiya and really not had a problem. But keep working at it you'll find a happy place.