I've seen a small improvement in comfort with ~week of regular stretching with this issue. I'm tucking my elbow in by my side at a 90 degree bend and presenting my sore wrist palm up. I'm then taking my other hand, grabbing my wrist and twisting it clockwise (my LH is twisting my RH). I'm either doing it as a passive stretch or, by resisting the twist, extending under load. I think. Might graduate to something weight based in a few weeks, but unsure about how that's going to work—I think it's something like the loaded extension of the "accelerating a motorbike" type movement.