For what they are worth. This applies mainly to the Testors line of Acrylic Paints. But it may also apply to other brands.
First of all.Testors Acryl is not as "user friendly" as Polly Scale. It should not be reduced with anything other than Testors own brand of Universal Acrylic Thinner. It has something to do with the paint formula Testors uses. Even distilled water will adversely affect it, reducing its ability to adhere to plastic.
Secondly. The first coat to go on a model should be applied "wet". My usual method with Polly Scale was to air-brush a few light "mist" coats first, give them a few minutes to dry, and then apply heavier coats. This does not seem to work as well with Testors Acryl.
This was learned by accident. I have started using my old Paasche model H again, and I was practicing with some Testors, using it straight from the bottle with just a few drops of their thinner. The Model H gives a courser, less "Misty" spray than my expensive gravity feed tool. So the paint was quite wet when it reached the surface of my old Paint Hulk. I learned later that the paint adhered better than it ever had before. Not peeling off with masking tape.
Well. That is all I have to say. Maybe this will be of some help. Maybe not.