Some good exercises are:
Deadlifts, single leg deadlifts, bridging, prone hip extensions, standing hip extensions with theraband, walking lunges, squats, single leg squats. All these you should be able to look up
Sorry really don't have much time at the moment.
If you have been regularly cycling and still don't have good glut activation, you may have to look at your seat height. Raising your seat height can decrease the load on your quads and gives a better length-tension relationship for your glut max activation for most day to day activities. Some cyclists have very good gluts then wonder why they have problems during the day (it's because of the sitting position while riding, teaches the gluts to acviate very well when on a long length tension, but they perform inefficently when in a standing or similar position when you don't have large degrees of hip flexion).
So try raising your seat height if you can do it comfortably, stretch your hip flexors and quads (should easily be able to find these on the net), and try running through some of the above exercises. I will report later on if I have some time with descriptions/sets/reps/weights/ways to progress exercises/links to pictures etc. if I have the time.
Keep using the tennis ball to release as well
Have to jet, sorry, musculoman!