I usually mark the end of my backing with an orange cone and place it on the left edge of the road
My wife is great at helping me back up. I tell her that I only want 4 signals from her to tell me which way we want the rear of the MH to go. She positions herself at the left rear corner and walks backwards. I don't move unless I can see her.
The signals are:
Pointing to the left
Pointing to the right.
Fingers on her hand up, palm in, waving towards her.
Hand raised fully, palm out, to tell me to stop
She forgets that I have a microphone at the rear of the MH, and I can hear what she says under her breath.