twiddling

Hello, i can twiddle with shakehand but i dont understand how to twiddle as a penholder. At 14:10 for example he serves and than twiddle to his short pips but i dont know how you move your fingers and so. Is there a tutorial or so for it?

I primarily play rpb penhold, and given that most information is Chinese, and that is penholders are constantly seeking innovation in terms of our grip, a thread seemed appropriate. Atm, I still block using tpb, but primarily avoid this stroke, playing a much more ma Lin and Xu xin inspired...