Reddit mentions of The Barber's Edge (The Barber's Edge): Cut your own neck hair and neck line with this template.

Hey, I think you really have to try a few things in order to figure out what works best for you. My personal opinion is that a shorter uniform cut is better.

If you want to try it longer on top first, that's not a bad idea. However if you don't like it, you can just even it out. If you don't like that, you can go shorter all over. Don't be afraid to experiment a bit; it'll grow back! You can take a bunch of pics at each stage so you can compare them later. I started buzzing my hair mainly because of thinning, but my temples are, I think, similar to yours. I find that a shorter cut works better for me.

If you have your own clippers, you can just easily do the uniform cut at home, as you can't really screw it up. I haven't been to a barber since I started doing it. You can also get tools to help with cleaning up the back. I've been using this one, although I found it hard to use without multiple mirrors. There seem to be better-rated tools out there for this.