Tight hip flexors are a product of too much tension... Adding more tension via the hip snap would be counter productive, that is if your goal is to relax and open up your hip flexors...
If it were me, I would work in some specific yoga poses to address your spot "issues."
Half Warrior, or Lunge
Pigeon, Reclining (or sleeping) pigeon, King Pigeon
Standing Side Stretch
Half Pyramid, or Pyramid
Side Angle Pose
There are more, but that should get you started...
"Who cares if your "deadly art" was originally practiced in a temple in some obscure corner of Bangladesh if an ill-tempered girl scout with 6 months of boxing can knock the hell out of its practitioners?" --Mike Driscoll