As others have said, backing is just a matter of "practice".
I "always" back by myself. I don't want the distraction of someone "helping" me.
My exception to that rule is for instance when backing the 35' horse trailer at a show. I have a spotter back there to make sure no children ( or adults for that matter ) get in the way. The ONLY thing I want to see from my spotter is the signal to STOP. Nothing else, ever. And this silly nonsense of people who use a their tiny little fist balled up as the "stop" signal does not cut it with me. We use the standard FAA signal for indicating the stop of an aircraft on the ramp: arms crossed above the head. If it's important enough to indicate a stop, then it's darn sure important enough to have a signal the driver can really see. That is something that can be seen from quite a distance.