This is a great video from Forrest Chang showing what Jin is in Chinese Martial Arts and how it can be used.
As he explains in the video, he calls these “stupid jin tricks” because they’re the sort of thing a teacher would look at you like you’re stupid if you asked him to do them. Somebody trained in internal martial arts should just be able to do these.
There is another thing that’s worth pointing out that he doesn’t explicitly state, but which should be obvious – there’s one jin.
All the early books on Tai Chi that came out in the 80s started listing all these different Jins, and I think that’s lead to a lot of misunderstanding that they are all separate things – when in reality there is one Jin in Chinese martial arts, and lots of ways of using it.
Once you’ve got a handle on what he’s doing it’s worth watching videos of famous teachers of Chinese Martial Arts and trying to analyse what they’re doing from a Jin perspective. I find their own explanations are often not very clear, so it’s better just to watch what they’re actually doing:
Chu Shong Tun (Wing Chun)
Sam Chin (Zhong Xu I LIq Chuan)
Adam Mizner (Tai Chi)