I drive while towing. She spots while backing. No talking. Just hand signals. We always come in during daylight, so as long as she stays in one of my mirrors and I have a basic lay of the land of the site before I back up, it works great.
I just watch where the trailer tires are going and that's where the trailer is going to go.. She basically just tells me when to stop so the trailer door is where she wants it in the camp site. That's important!
Anyway, works for us... Have heard the yelling back and forth on too many couples backing in.. Makes for some entertaining people watching for sure!
Just like watching folks at a boat ramp... Very entertaining..
I've also seen some very nice walkie-talkie work backing in and they nail it on the first try with just very basic voice commands... So, it really comes down to what works best for you as a couple and gets you in without yelling or having to take 20 minutes to get into your site!! :)
Good luck!
Mitch