For me its Vallejo. The eye dropper bottle make life easy to load an a/b and to add drop by drop to get the right consistency with Vallejo thinner. The Air range do not need thinning of course though I sometimes do thin a little (80:20) or more if I am shading.
Wondering Alexander. Does this happen when you are airbrushing large areas or when you are applying for example WW11 camo on German Aircraft, ie the "blobs" ?
Also does this happen when you first start airbrushing or is it during a session ?
Also is your compressor a tank or tankless type. Had problems with a tankless compressor recently which gave similar problems ie unbeknown to me, to start with, the air supply was not consistent & I was getting some splodges & also blockages.