As tempted as I have been to describe the various methods I tried and what I finally came up with, I'm trying to make and sell ultralight products so I guess it's proprietary.
Not that it would be easy to replicate, since it required access to a full metal shop (my Dad's). Trail Designs told me their method is proprietary. It never occurred to me to ask Dan how he does it, but I think I remember a post in some thread where someone asked Dan how he did it and he declined to reveal his method. If my recollection is wrong, I stand corrected.
I will say that I tried a couple of commercially available bead rollers, and they did a very nice job of crinkling and cutting the cans. I gave some thought to making custom dies for one of the bead rollers, and may still try it, but it doesn't solve the problem of making multiple ridges at the same time with precise spacing to indicate the fluid levels. Nor does it resolve the issue of the BPA plastic lining.
I will also say that some of the key parts are available at any well-stocked hardware store, and part of the process can be duplicated in most kitchens.