膀手：feel shoulder move，not elbow； imagine a line between shoulder and wrist; when a weight is on forearm, come back first like holding a ball to avoid force, then do 膀手；
栏手：feel the whole forearm, focus on the middle point, move the point; image an air ball between the arm and body. same as moving knife, the middle point, as if there is no resistance.
knowing where the hands go, body follow the hands move to support them.
don’t let hand fold, which will make the forearm tense, and fall the ball.