Self-myofascial release is a great way to increase hip mobility via decreasing fascial restrictions within the muscles crossing the hip.
Skip to the 2:50 mark here for a video demonstration.
When working on the quad group, we are specifically interested in the rectus femoris, which is the only muscle in the quad of group that crosses the hip.
Get a lacrosse or baseball. Don't go till the point of bruising.
There should be no numbness or tingling created. Move the joints above and below the balls contact for added benefit.