I have three exercises that I go to when I have an achey lower back and hips - the Bulgarian Split Squat, Windmills, and Cossack Squats. Sometimes I'll do all three as part of warm-up, and sometimes "the warm-up is the workout" (Dan John). Let me know how you find this trio if you decide to try them after reading this.
Bulgarian Split Squats: Although some go quite heavy, I don't think I've ever used over 135lbs with the exercise - in my opinion, there's just too much that can go wrong quite quickly. Even with just bodyweight and high reps (20+/leg), it's tough to beat for waking up the glutes and working the hip flexors through a range of motion you don't get with other exercises. I do mine a little differently and like to keep the ball of my back (elevated) foot in contact with the box/platform - this seems to keep the back leg in the game more (for me).
Windmills: I've always loved this exercise. It's like a good morning on a different plane of motion. Kicking the hips to the side, chest out, and only descending as far as you can do with good form are key. I don't go very heavy with this exercise either, but I like to use a 16-32kg kettlebell and do 5-10 reps/side.
Cossack Squats: I've been doing these (off and on) since I was 10 years old in Mr. Pak's basement, warming up for Tae Kwon Do class. Getting the groove can be difficult and should be done to a shallower depth with some kind of assistance (like a TRX or the support beams of a power rack, for example) until competence and confidence is established.