This is like a concentration curl for your butt. Here's how to do it.
Place a foam roller under one leg. The closer you place it to your knee, the easier it becomes. Placing it closer to the foot lengthens the leaver and makes it tougher. Using the foam roller puts you in a fail-proof position that forces glute recruitment and takes out most of the hamstring work.
Before bridging, drive the leg straight as an arrow, squeezing your quad while dorsiflexing the ankle (raising toes toward knee). It's only a 3-4 inch bridge, but it's damn effective. Just 1-2 sets of 10 to start a lower body workout will activate the hips. Or use it for higher reps as a finisher to your lower body workout.