B
Boston Mike
Guest
Beyond exercises I'd say just find a project you like and want to do and dive in.
Airbrush tutor has the eye in versions from basic to more advanced, and Cameron Diaz and some other good ones.
There are some good step by steps here too.
Feeling inspired goes a long ways so if you find or think of something really cool go for it.
I'm always most inspired to paint a beautiful lady
Whether that's a painting of...or a painting on her.