I am completely asymptomatic, pain free, and perform extremely high stress and high flexibility athletics. Here's how I do it:
- hip raises on the ball[1] 20-30 reps.
- scorpion stretch[2] - 20-30 reps, back and forth.
- roman chair[3] - 40-50 reps, some with a weight across chest
- plain old straight leg deadlifts with dumbbells
- and of course, balance it all out with ab and trunk strengthening
But, BUT ... the real key is walking. Your body is a machine built for walking. You may scoff, but nothing nothing will tighten and straighten up your back, and all of its supporting muscles, and erase the imbalances and create the alignment you need more than walking.
Walking will heal you. The first week or so might make things worse - a LOT worse. Just keep it up. The walking will heal you.
[1] http://reach-yourpeak.com/tag/glute-strength/
[2] http://www.jsonline.com/multimedia/video/?bctid=64438317001