I put these into action after finally getting fed up with my head getting shoved forward in the squat for too long. -
They are pretty self-explanatory. Getting in can be a little tricky so pay attention to the video.
Keep your feet straight ahead, don't go duckfoot and turn your toes out. Keep your feet apart. Hunch your back when lowering the weight then arch your head and back and squeeze your glutes to raise it.
It may take a couple reps to get your rhythm down. Try to flex your entire posterior chain all at once. If training athletes this is great for efficiency as you're killing two birds with one stone. Keep the harness weight light.
Sets and reps range from 3-4 x 20-60. Many of the muscles involved are primarily oxidative or postural so we have to train them in high rep ranges. If your neck can't handle 60 reps simply do as many as you can then hold it statically while your legs finish the reps.
This made a big difference in my head positioning on my squats within a few weeks.