just comment on something in theory.
1. the neck has to be suspending as if the head is hanging up, (tou ding xuan) meaning to reduce or absorb most of the energy before it reaches the head. too much energy to the head or shaking is not good for the brain.
2. along the same idea, the energy from the stomping feet would dissipate and not concentrate on the groin area, one may become sterile.
3. as for issuing power, true, the outburst from dan tian then toward the limbs, the final shaking is either all body shaking or just fist or palm shaking/vibrating meaning the power passing thru wrist so only the hand is shaking and not the forearm, meaning we focus on expressing toward the end.
think of this way, if you want to push or punch, if most of your power is expressed on the hand, and not wasted on shaking the forearm or the shaking the head?
a. the whole body shaking is actually gradual progression, from dan tian toward the hands and feet, we may not see the waves, but you would see the "outburst".
b. focused expression is explained above.
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as for the apps.
1. when he tries to catch the punching arm with his both arms, his face is exposed or not guarded. so maybe move back a bit, and catch around the wrist or forearm area of the opponent first, then deal with the opponent's elbow. (at 6:41)
2. when he bends the opponent's elbow, the opponent may actually move forward and introduce elbow forward and downward strike to his abdomen or chest. or the opponent may turn his left side closer, and may use his left hand/left shoulder/left chest etc to push/strike An's shoulder or back to make An fall or use left elbow to strike An's temple etc (at 7:27)
just to add some thoughts.
thanks for posting.