I think that focus is the key.
I have been at this for a couple months, and have made gains, but I still feel that I have yet to completely get the hang of it. It seems like it would be easy, but it is not.
As my erection level does not stay constant through the jelqing session, I have to vary the amount of squeeze according to the erection level at the moment.
I also have to make sure I don’t go too fast, and always reminding myself not to squeeze too hard.
So I agree, you can’t just yank away, you have to pay attention to what you are doing with every stroke.
If you don’t, you are definitely not getting all the gains you can, or you might be yanking away and not get any gains.