Then select the LowerArm01 bone and Right-Click and click on Wire Parameter -> Transform -> Rotation -> Keyframe XYZ -> X Rotation to the CTRL_Wrist_R's Transform -> Rotation -> Keyframe XYZ -> X Rotation.
After that the Wire Parameter Dialogue box will pop up. If you followed the previous instruction, the CTRL_Wrist_R should be in the right window, you then click the arrow facing to the left and in the Expression for Bone_LowerArm01_R x-rotation type in X_Rotation/2 and then click Connect.
THAT'S IT!!! Finally, finished, take a look at the next picture and you'll notice that the hand bone has been rotated 90 degrees and the LowerArm01 bone has rotated half as much, so once you skin your model, that will help with stopping that ugly deformation in the wrist. Just make sure when you add the skin modifier to your model, make sure you add the BONES, not the DUMMY objects. Hope that works for everyone, and hope it's useful. Any questions or comments, you can e-mail me at [email protected]
That is the skinned version of double rotation, if I had my model textured it would make much more sense, but please trust me, it's there and it helps out a lot.