One very simple way works well with core muscles, lower back, buttocks etc.It is also very good for lower back pain in general, but not all types.

Do a few hip circles i.e standing upright and moving your pelvis in a circle. You want a variation of that; place your hands 'on your hips' this is actually the top of your pelvis (the Iliac Crest), you should feel the hard bony pelvis under your hands. Now, focus where your hands meet the pelvis, this is where you want to create the circling motion (rather than the hips in your original trial).

Do a dozen clockwise then a dozen anti clockwise, 3 times a day. Increase the quantity as you grow stronger and more confident.

Al- Sport and Remedial Masseur.