There are several ways we can target the hip area, but first we need to understand what is meant by "hips." It is a very vague term and anatomists prefer to be more specific. Do you mean the "hip socket" known as the acetabulum where the femur inserts into the pelvis, or do you mean the top of the wings of the pelvis, what is called the iliac crest? (Your belt hangs on the iliac crest while your back pants pocket ends near the acetabulum.)
If your intention is to target the area around the iliac crest, try Bananasana, side bends while in Shoelace or Half Butterfly, or Reclining Twist with the top leg straight out to the side. If your intention is to target the hip socket, try Shoelace, Square, Winged Dragon or Swan poses. You can check the Yin Asana
page to view these poses.
Remember, if you are feeling it, you are doing it. In Yin Yoga time is more important than intensity. You don't have to be at the maximum intensity for the pose to work its magic. Also remember, Yin Yoga is just half the equation: I would suggest you also keep doing some yang exercise for these areas too - standing poses like Triangle, Warrior Two and Eagle may be beneficial. Combining these with some core work like Crocodile, Boat and Locust poses could be very good for your lower back.
Good luck. Let us know how it goes.