There has been some good advice posted here. I'll just suggest a couple of additional things:
When I first started, I just couldn't figure out a way to file the right-hand cutters with my right (dominant) hand. So I made myself learn to do them with my left, and it was pretty easy after a bit. That was 30+ years ago, and now I'm at least as good with my left.
Last winter, a member here chased down some of the new Oberg double-bevel chisel files and got some for me. I honestly didn't expect much, as they look just like all the others currently available. I've tried everything I could find in the last few years. I used ONE of the new Obergs exclusively for the whole summer. (It's been years since I logged, but I cut a LOT of firewood.) One file has done the job for the entire summer and finally met its demise a few days ago. I had a chain left here by someone who didn't pick up his saw or pay me, so I converted the chain to square for my own use. The chain had been ground and hardened, so it was rough on the file. It's still a good depth gauge file, though. Still not 100% sure they're better than others, but I can only say one bad thing about the new Obergs - I like the old ones better.