While I do most of the driving, we make sure to switch out once in a while, so if something happens to me, she can drive the rig.
All this talk about "skill set" is just silly. It's not rocket science.
As far as backing, we use hand signals. Seen plenty of walkie talkies start yelling for some reason and one poor lady almost run over when she stood behind the trailer giving directions to keep coming back...then tripped and almost got run over.
With hand signals, if I can't see her, I hit the brakes. (again, I usually do the backing but we do switch out occasionally for practice)