HOW: Start by holding a long towel while standing fairly close to a wall to the side of you. Begin by stepping laterally with the outside leg away from the wall. Load that leg up by slightly bending the knee, hinging forward at the waist, and bringing the towel down towards that leg. From here, push into the ground with that outside leg and begin to whip the towel into the wall with your momentum going towards the wall.
FEEL: You should feel your leg and core muscles working the most.
COMPENSATION: Make sure to keep your hips perpendicular to the wall even while whipping the towel.