The team of fitFLEX highly suggests you stick to movements that stress your glutes and hamstrings. The parallel and half-squat will build your
glutes and entire leg. Leg presses with an extra wide stance and the feet at the top of the platform put nearly all the load on the glutes and
hamstrings. There is also a special Vince Gironda glute-builder you can do called "buns-out squats." These are really a combination of good
mornings and squats. Use about half the weight you would for regular squats. Take a wide stance, bend at the waist as you descend, and make a
concerted effort to push your glutes or "buns " out as far as possible. Do higher reps - say, 12 to 20 - and try for a burn in the glute area.
These are movements which will add needed size and fullness to your glutes and legs. For hamstring specialization you must do leg curls - seated, lying, or standing one leg at a time. Lunges, stiff-leg deadlifts and good mornings also work the glutes and hams at the same time, as do hyperextensions if you consciously target the glutes where they tie in below the lower back.
One-leg cable kickbacks, using the lower cable of a pulley machine and a special ankle attachment, are a terrific shaper and builder for glutes. Do high reps - say, 4 sets of 15 to 25 reps for each side.
Another activity that helps to build and tone the glutes is speed walking on the treadmill with the slope at its highest possible height. It's like speed walking uphill. Your glutes and legs should burn after this one.
Since upper-body work is not important for you, I suggest you train on a three-day-on/one-day-off routine. Do all your upper-body movements on day 1, all your quad and glute movements on day 2, and all your hamstring-glute movements on day 3. You might, for example, do squats, leg presses, buns-out squats and lunges on day 2, and leg curls, stiff-leg deadlifts, good mornings, hyperextensions and cable kickbacks on day 3. You can train abs and calves every other day. Do your treadmill work four or five times a week as needed.