One last post on the BUTT wink. I find myself saying to others contract your core and pull down into the squat. After some reading it seems that it's pulling down via the hip flexers that allows the squatter to fight the BUTT wink.
1. Be tight and pull down into the squat so that every muscle in your body is working.
2. Use a ball to stop from going into the butt wink. Yet, don't get addicted to the ball. You can also ask someone to watch you and tell you when to stop descending and power up.
3. Wall squats
5. Windmills or movements that work your hamstrings without making your lower back overly flexible.
I've not talked about it but I do see a connection between forward lean in the squat and butt wink. People that have one or the other most of the time have them both.