I think there are few variables that make the difference between a successful hanging session and a bad one.
The penis is different from person to person and we can even find big differences between the state of our own penis from day to day even hour to hour.
The head of the penis is what allows you to grab your penis when you stretch or hang.If the head is small and soft and the corpus of the penis is tough and thick,there is no way you will be able to get a good grip on that thing.The skin is something that rides over the internal structure so it slides no matter what you do instill it gets to the head where it should stop.
There are very different types of penis shapes out there so concluding that someone has a bad technique is irrelevant unless you tried to hang having his penis.
My experience tooth me that before a good stretching or hanging session I should work to get an engorged tough head and a soft and thin corpus.