If you have a good working setup with ik_hand_gun, dont switch to a socket on the hand, that would be a downgrade. Setup blend masks. For example mine has spine_01 all the way down to the fingers set at 1.0, then all the ik_hand_x bones are set at 1.0, pelvis and legs are set to 0.0. What I do is I have a virtual bone on the head of my skeleton, at the start of the anim graph I do CopyBone to move that VB to the ik_hand_gun bone, run all my procedural logic on the VB, then do the layered blend per bone using the mask, then use CopyBone again to copy ik_hand_gun to the VB
