I think everyone just has to find what works for them. If the OP thinks walkies will help, then he should try them.
For us, at least so far, it has worked very well for me to scope out the site before backing in, then backing in myself. DW does stand behind the TT as a spotter, but her sole responsibility is to holler, and holler loud, if I am going to hit anything I didn't see or anticipate. I always back with both side windows fully open, both so I can hear DW, and to get a clearer view through the mirrors. Even with DW not with me, such as when I just take DS, I still have both windows down.
I also ask DW to stay within my passenger side mirror view as much as possible once I straighten out and am backing straight in. This way I can see that she is indeed looking out for me (that she's got my back, so to speak).
