These have helped me:
* contrast baths, a few times a week
* sweatbands for the wrists, just for extra warmth
* thoroughly SMR'ing the neck, biceps, forearm, and hands with a golf ball
As far as rehab exercises go, I like the forearm roller, while holding the weight out in front of you. Do it both "forwards" and "backwards" and don't skimp on the eccentric. A 5lb plate ought to be plenty.
I felt like the rice bag did more harm than good for me. It's too easy to overdo it (either in duration or depth/"resistance"), I think.
And yes, I'm actually holding that handstand. Get on my level.