Spotting.
Always get out. Make sure he has the windows down so he can hear you.
Tell him the back-up camera can't show him where the wheels are, nor can it show overhanding branches which can damage the rig. I've seen an AC pulled off a 5er while backing with a backup camera.
One of my best, most experienced friends managed to catch the curbside rear slide cover awning unit on an overhanging limb and pull that off the motorhome - while going forward to get into position to backup a few months ago.
Everyone can use help in backing the rig into a spot.
