It takes a while to practice. First of all, you should get more contact with push-ups and parallel bars, of course, if you have arm strength devices and tensioners to help you practice. Then let your pectoralis major and deltoid muscles develop, and often spread your wings to help the deltoid muscle in front of the armpit feel twitchy, which will help the pectoralis muscle shake.

How to shake: When sitting on a stool without a backrest, put your hands on your knees naturally, and your head is slightly lower (you can see the muscles shaking), but not too low, which will affect your movements. Slowly shake your anterior axillary muscle (the front of deltoid muscle), so that pectoralis major will also move with the action, so that you can shake it.

Note: you can't practice hard because of "temporary heat", which is not good for your muscles. You should do it step by step. Have confidence in yourself. At first, the movement was small, and the movement range was not large. Mainly the method is not important. The method is right, and it will be effective if you practice slowly.