Corkscrewing/ turning over the knee.

This is a question on knee strikes. I'm terrible at knees. So watching youtube I have came across before a detail with long knees about corkscrewing your knee so the foot it to the outside, to give you more range, and to drive your knee in harder. These two video explain what i'm talking

But I still have trouble with this. This is not the way I was shown to throw a knee, but It seems a better way. I have trouble getting my foot to the outside/ corkscrewing my knee. Is there a video explaining this better or any tips, drills on how to achieve this easier? Its odd to ask for such a simple question and technique , and I know the obvious answer is to practice more, but for whatever reason I still have trouble with this even being pretty flexible.

How much are you stretching? How old are you?