I've been doing a new exercise where I attempt to do a study (from photo) with a limit on the number of brushstrokes I can make. Each of these was between 20 and 25 strokes. If i lift my pen from the tablet that counts as a stroke. I am making use of all the other tools freely however. Selections, transform, eraser, smudge are all paramount. It's been a nice way to force myself to plan ahead, stay focused on the important elements, and make the most of all the other tools available.
I'm thinking of trying another set with a higher limit, like 100, but i'm not allowed to use selections or erase. It'll be harder I think!