Ultimate Modelling Products out of the U.K. Acrylic thinners and airbrush cleaner, wax and shine, polishing compounds and decal set. The decal set is available in 3 strengths. Naturally, some experimentation will be needed to determine your particular job. The extra strong will ensure those stubborn decals sit, it's very aggressive. I use it and it comes highly recommended. I have linked a couple of Youtube videos below with Paul Bretland demonstrating the airbrush cleaner and decal set, I hope you find them as useful as I did.

"How to use" Ultimate Modelling Products Decal Solutions - YouTube

How to Clean Your Airbrush Cup Tutorial - YouTube