The hip flexor stretch (PAIL/RAIL) can help you to improve your hip extension and glute engagement. It can also help you to get proper movement through the hip without compensating through the lower back.

1-2 minute stretch - deep diaphragm breathing into the front of the hip
10s + PAILs contraction - slowly ramping (20%, 40%, 60% +) up a contraction in the tissue we are stretching (hip flexors)
10s + RAILs contraction - slowly ramping (20%, 40%, 60%+) up a contraction in the opposite tissue (glute and hamstring)
** after releasing the RAIL contraction you should gain 15 degrees of range, you can hold in this new range and repeat the process:
30s stretch - in the new position
10 sec PAILs contraction
10 sec RAILs contraction

Caution: if you are new to PAILs and RAILs contractions start at 20 or 40% and and work on your stretches 5 days a week, once you have the feel and have increased you tolerance you can increase the contraction 60%+ and reduce your days to 3 days/week.