The classic technique since Tong Fei popularized it in 1985 is well explained in this Lee Woolls tutorial.
Click PLAY or watch it on YouTube.
On the other hand, some Chinese coaches are now greatly reducing the severity of the action.
A huge tap is not really necessary. It’s usually a form deduction at the bottom of the swing. And there have even been injuries to the lower back from excessive tap.
Gymnastics Coaching.com 