Grabbing the Mane or a neck strap (a stirrup leather around the neck braided in the mane to hold onto
Something to do while not on a horse would be on an exercise ball. Practice balancing and getting into that position you want.
With an injured hip you don't want to push anything. Rising for 3 beats instead of one in the trot will help with balance because you will have to focus on not allowing yourself to naturally fall back into the saddle and is a really good exercise for balance. You can also try going in your two point over poles and going into two point without stirrups at walk and trot.
Having someone else take a video/picture of you in the 2 or 3 point will also allow you to see where you a struggling and what you need to work on.