I have a similar problem. I only have a small compressor with no reservoir but it does have a water trap. I found that because I bring the compressor in from the garage to use it, and there is a long hose from the compressor to the
airbrush, the cold air was condensing and causing water spatter. I have seen some articles that advise pointing a fan at your compressor to keep it cool. I suspect my science may be flawed here, so feel free to correct me! Generally, I tend to bring the compressor in an hour or so before I use it, then connect eh
airbrush and put the compressor on the table, hold the
airbrush lower that the table so any water molecules in the hose can run down to the
airbrush and give it a good blast into some tissue. It seems to clear the worst of it but after a while using it I get the odd spit. It only needs the tiniest amount of water to create a big splat so I tend to blast some air through before any spraying just to clear any potential drips. In the end it is hard to stop it happening but you can come to anticipate it!
Hope that helps.
Tony B