Any reason why you're adverst to using an airbursh? Its probably the right tool for the right job. You can find them pretty cheap - even a junky pache airbrush for Tshirt painting would work ok. I find that the thinner I can paint - the more fliexible the acrylic is and the less its opt to pull away or develop cracks.
You can also work to prep/clean your surfaces more to make sure that the acryic will bond to it better.
There are mediums out there (they go by differnt names) that you can mix to increase the flexibility and bonding properties of your acrylic as well. Seach the moster makers website and some sites for Tshirt / leather jacket painting - they'll have good paints and good additives you can use for better success. I've airbushed a lot of leather jackets and a lot of latex appliances and have experimented with many techniques, and additives really do make a difference.
Low quality Acryiic (yeah it does vary in quality) applied too heavily/thick will get less flexible and crack more than a thin layer of acrylic applied with an airbrush to a good clean surface.
Cathat
