nothing has helped me with my butt wink more than a groin stretch. this may be just me though.
I found this out accidentally. I was in the power cage and holding on to one of the sides, while trying to squat down and REALLY FORCE my lower back to stay straight. this was made easier by holding onto the side of the cage and leverage with my arms. what i noticed was that when i got to a certain point, i felt a little groin stretch... then when i went deeper into the hole, the stretch disappeared and my butt winked.
i realized my groin was too tight allow my lower back to stay straight as my hips went into flexion. i stretched my groin for 5min straight after that, then tried the squat thing again (with my hands on the side of a cage, holding on, applying leverage to flatten my lower back) and i was able to go deeper.
ill check this vid out though. sounds great.
