Another concept I got from the video was to rotate the elbow. In order to lead with hand, you needed to find a spot for your elbow, at which it could be rotated. Once the spot was located, it should not move. Lead with hand, and rotate the elbow. Locating the right spot for the elbow might involve aligning the rest of the body parts.
Foot - striaght to the ground
Knee - rotate empty (meaning no displacement, but just transmit the energy)
Thigh - rotate horizontally
Waist - adjust
Shoulder - rotate down or up
Elbow - rotate sideways and lead in
Hand - lead out