If airbrushing with acrylics I use a home brew of thinners, comprising IPA, water, flow retarder and flow inprover. I stop and clean the airbrush tip regularly. Enamels are more forgiving for airbrushing in my experience, in so far as they are less likely to clog the airbrush. The drying times between coats is one advantage of acrylics. I've been able to apply several coats in a day sometimes, whereas with enamels I leave days between coats.