I did the exercises once a good few months after I started messing about with the airbrush. I did better at some than at others. I would rather practice whilst I am airbrushing a picture and i can tell you, for me this seems to work just fine. I will probably try them again in a few weeks and I imagine I will see if im improving or not. But really, like what was mention above, I have been doing these exercises the whole time when I paint. Blends, dots, moving dots, the lot.