Do bird-dogs without lifting your arms. From the quadruped position, lift one leg straight back so it is parallel to the floor. Lower it back to the ground. Repeat with the other leg. For maximum results, place a dowel rod on across your lower back and do the exercises without the dowel falling off. Focuses on activating glutes without rotating hips. Can do 100 of these a day as this is neuromuscular (activating) and produces best results with maximum volume.
Do 1 legged bridges but with your knee held to your chest. Lay on your back in a situp position. Pull one knee to your chest and hold it tightly in place. Squeeze your glutes (not hamstrings) and lift up into a bridge position so shoulder to knee is a straight line. Hold for 3 seconds. Lower. Repeat. This is a strengthening and activating exercise but it can cause strain on the lower back and hamstrings if not done correctly. Start with 1 set of 5 to each side. Increase up to 3 sets a day once you are ready. Once you can handle 3 sets a day, increase the reps by 5.
For stretches, do the newspaper stretch. Hold for 3 minutes per side in order to lengthen the muscles. 30 seconds will make you feel better but more time is needed to actually lengthen the tissue.