Attached Link: eclipse studios

This  tutorial shows you how to link one hand to a prop that has been parented to another hand. An essential technique for motion capture sequences where the imported motion capture is driving the IK of both arms and hands. This is applicable to sequences which require both hands holding an object such as a gun,axe, sword, staff, etc. To achieve a realistic animation, both hands need to grip the object and not move or slide, an effect that is pretty much impossible without using this technique.

This tutorial includes a sample motion file in Poser .pz2 pose format,of a man walking with a rifle
and 2 animation clips showing Michael 3 with a rifle parented to the right hand, before and after the
technique is appled.
 
Tutorial can be found at
http://www.es3d.com/tutorial/

.swf of completed effect
http://www.es3d.com/tutorial_2hands_after.html