Same here. My final straws were 1) my regular local barbershop suddenly disappearing on me, while I was still holding a few of their discount haircut coupons I had stupidity to buy in advance (let this be a lesson to you folks), and 2) tried another shop and saw in horror how dirty their tools/accessories were.
So being a DYI guy, I watched a few YT videos, bought $20 electric clippers, made my share of beginner's mistakes, but now I really enjoy getting better at it and won't go back at any price.
Yes, the back of the head is the hardest part. When I don't ask for someone else's help, I try to choreograph the movement I saw in a video: put my other hand horizontally to limit the range and move the clipper in a precise fade-out manner, bottom-to-top. I like it short. Use 2 mirrors and don't hurry.
You can use a comb or a stencil to make a line and carefully follow it. If you have good dexterity and flexible mirrors, you can do it by eye. Or if you fade to 0 length you may not need to cut a sharp line depending on your style.
So being a DYI guy, I watched a few YT videos, bought $20 electric clippers, made my share of beginner's mistakes, but now I really enjoy getting better at it and won't go back at any price.