To work on adductor/internal rotator flexiblity you can try some of the following:
(however if this doesn't stretch the affected limb, keep reading)
I've used the first of these two styles, although I like to put my feet flat against a wall for leverage and shove my hips horizontally backwards. In my experience, the second style requires enough flexibility to butterfly correctly (and thus not very useful to me yet), but I could be wrong. You might try PNF by contracting the adductors, shoving the hips back, repeat. Maybe widen the knee position during the PNF session as you get looser.
Check out the full article "The Hockey Groin"
3) Groin (adductor) stretch – While kneeling on both knees, take the knees as far apart as they can go within your pain free limits. Lean forward and rest on your elbows. Keep the arches on the feet flat on the ground. Keep the back straight and lean slowly backwards towards the feet until a stretch is felt in the groin.
Terribly painful, but highly effective. I'm slowing working up to it. Full article by Thomas Kurz here.
I'm trying to emulate this kind of setup:
A partner is ideal, but let's assume one's not available. Grab a plate and head over to the stall bars (or any sturdy structure close to the floor). Lie down parallel to the stall bars, put the weight on the femur/knee, and take hold of the stall bars. Pushing and/or pulling on the stall bars functions as the PT's right hand, counteracting the body's desire to just rotate over. The weight serves as the PT's left hand. Relax/PNF away. Also consider crossing the weighted leg's ankle over the other knee.
Another option is to shoot for this setup:
with two weights (or a partner), but I find that I get a better stretch attacking one leg at a time.