I honestly thought I'd addressed this before. But, I'm more than happy to provide input towards an assumption of skillful teaching.
1) Skillful Teaching is Whatever Helps Students Learn
This is one of those ambiguous statements that slightly bothers me enough just to bother me. It's a little vague, and involves a lot more digging than skimming over the surface. This is almost like saying "skillful driving is whatever gets us from point A to B".
Using the car metaphor, a skillful driver will know where they're going, what controls to operate, when and how to operate them, but most importantly why. For example, what gear to be in while going up a hill on a dirt road, while maintaining the correct angle of the steering wheel and giving just enough throttle to keep the car accelerating but not lose control.
As Brookfield states, "If we take this assumption seriously, it means our teaching becomes more, not less, complex." (Brookfield, 2011, p. 18).