A machine of some type will do it the fastest and the truest and it can be done by hand makeing them the same profile by hand would be quite the challange being true when your done is what you will want when you are finished and the correct size you are looking for good luck !
That isn't cutting tires though, thats just resurfacing them. He's asking about how to cut them by hand. The bondo file works good once you get the hang on how to use it. At Autozone they sell a bondo file with a file holder for about 8 bucks, thats what I use.
I personally do not cut my tires. Todd Wills at Edge Cutz does cuts my tires with his Jones. So I'm of little help. Cut them once then just resurface weekly. I do the resurfacing. Just a 4 1/2" grinder and a 60grit disc. Spray the tire with racing alcohol to keep it cool surface then wipe down with acrysol. Let dry and put a coat of prep on. That's my method.
What RPM are the actual tire cutters spinning at? Not the tire surfacers with bondo files. Ive got a buddy with a lathe who is going to do it for me but hes never done tires. I ordered a bit from carlson.