You'll have to look for a retarder product, usually found in craft stores. I've never used it, but it would be wise to try it on some other surface to see how well it reacts with different paint brands you have.
Another option is to airbrush your main colour first, and rely on this as a primer coat at the same time. If you want to go further with the airbrush, mix a darker shade of the main colour and spray from underneath, catching the shadow areas. Follow this with a lighter shade mix and spray only from atop, like a light source, this would represent highlights. Then you can go in with the brush for finer details.
regards,
Jack