What I used to do was a #2 guard on the sides and a #3 or #4 on the top.
I made a folding 3 sided mirror out of some mirror tiles at home depot I used to try and help.
Tried to get sharon to do it but she didn't get the feel of the clippers and would somehow just rip the hair out of my head. I would have her try and clean up the back.
Seems way easier to just not cut it anymore, lol. Not like I go anywhere.