You model the mini figs hand onto the guns model, and then do this:
WeaponImageName::OnMount(%this,%obj,%slot)
{
Parent::OnMount(%this,%obj,%slot);
%obj.hidenode("LHand");
}
Once you equip the gun, it will hide your left hand, and the hand model on the gun will make it look like you're holding the gun with both hands, but then there's the fact of different hand colors.