So tonight when I was about to call everyone back into lines after stretching, a bunch of people were doing cetitui stretch after Shifu had been doing it with Randy and Khalid. So I thought, "Hey, that looks good, let's all do it."
Luckily for me I was the odd one out, so I asked Shifu to stretch me. So I paid attention to his technique. I got as sideways as I could, straightened my leg, and just relaxed. It would be great if everyone knew how to stretch people like he does! So he raised my leg up to where there was pretty good resistance (not from me -- I was relaxed, but from my leg), but I wasn't dying. I was still able to flex my foot even more. That's not to say I wasn't getting a good stretch though. Believe me, I felt it!
Maybe I should not train for 5 days in a row more often: I hit the middle split tonight and was able to extend my back up off the floor too. I know I'm gonna feel it tomorrow though!
But, anyway, he held that for just a few seconds, then brought my leg down and told me to relax more. Then he shook the leg around a bit to help it relax. He said, "Now can go more." And when he brought it up a second time, it did go up more.
After the second round, he told me to relax again, and then, using his chest against my foot, pushed my knee to my shoulder, still on the sideways axis. This was to counterstretch, and we do the same thing when we do zhengtitui stretch, or the butterfly stretch after middle splits.
When he did my other side, the knee-to-shoulder stretch really pushed it for me (my left hip can't open up much) and my right (standing) leg started to bend without me even realizing it. Shifu noticed and gave a light kick to my shin to remind me.
Oh yea and I didn't even tell him when to stop or anything; he just stopped because he could feel it himself. After you stretch with other people a lot you start to be able to feel their bodies just from holding them and looking at them I think. So stretch together more! :)

So to me it was the same as how we do multiple rounds for straddle stretch or anything, or how I get in my stretching machine around 6 then go out a bit, then a few minutes later come back again and go more. First round relaxes and opens you up a bit, but subsequent rounds are where you really go further. And each time, Shifu didn't hold it for that long. Maybe it was because we were in the middle of class and it was a time thing, or maybe that's just a good way to do it.
Try different things and see what works for you! Be honest with yourself and push yourself! Train harder!