What I term a "sweep" motion is often confused with rotation, but they are two different movements!
A sweep uses two fingers, like a rotation, but instead of rotating the forearm across a fixed point in the wrist, you are going to let the fixed point travel from right to left or from left to right. This involves some distinct differences:
- Start with alignment through the finger being played, just as in a drop motion.
- Let the wrist deviate to the right (or the left if you are moving inward) so that this point travels to the side.
- Use this motion to "walk" you over to the next finger being played and then gently release the wrist.
Sweeps can (and should!) be practiced between any pair of fingers going outward or inward.