Just as a sanity check, you should draw some debug axes for your hand transform. Rotate your hand in as many directions as you want, you should be able to see no pops in the orientation axes. Here is a quick blueprint to help you:
If you notice any popping when you rotate your hand, that means your hand rotation math is wrong. If it looks smooth, then you can take the rotation from your hand and replace the world rotation of whatever object you’re holding with your hand rotation. Keep in mind, that you’ll be rotating your object around its local origin.