We use our FRS radios when we’re backing the rig and I highly recommend them. Using the radios eliminates yelling and allows much more information to be exchanged between driver and spotter. As the driver I don’t normally have to say much so I turn the volume up and set the radio on the seat beside me.
If you don’t want to use radios then you and your spouse should have specific signals. To avoid confusion your signals should be distinct and deliberate. Use your whole arm instead of just waving your hand. The basic signals you will need are stop, left, right, straight back and distance.
You should agree what left, right and straight mean too. Does the direction refer to which way the RV needs to go or which way the steering wheel needs to turn.