"Swinging fist" ballbusting

So, while I like squeezing and knees, my absolute favourite is what I can only label "swinging fist".

It's not punching, it's not hamnerfist, it's not uppercuts to the sac. The effect is similar to the ball in a sock technique, but the girl is using her fist as the loose (but heavy) weight to repeatedly swing up into the sac.

There are very few videos featuring this technique sadly.

if there are any good videos you know of, please share. and also let me know if you can think of a better name!!