My airbrushed Aztek acrylic cracked over Testors enamel primer. Letting the enamel primer dry several hours wasn't enough time, probably. Perhaps a high humidity indoors (fog outside) played a role in the dry time. Just coated with Testors satin lacquor dullcoat and may airbrush over it, once cured.
So far, I've had better luck airbrushing Vallejo without a primer, though it'll peel when masking if not sealed first with Testors satin lacquor dullcoat. Nothing, not acrylics or enamels, stick to Testors gloss lacquor.
I'd like to spray Vallejo's acrylic primer and then spray Vallejo's acrylic paints, but the acrylic primer gummed up and jammed my Badger 105 airbrush. I may try to shoot the primer at a higher psi.
On a good note, my projects are already weathered before I go to weather them. :D