Most of this is done by the follower not really helping as much as she is cooperating. The leg must freely swing and echo the energy of the centripetal movements. Her core is strong, her spine is malleable, her frame is strong but soft and malleable.
The leader is generating energy and allowing this energy to flow from his frame into he woman’s with the same malleability as she has. These movements are the truest sense of partnership in that both partners must clearly be aware of their roles and surrender to the energy as effortlessly as possible.
You want to see the movements and not the work behind them.