Like D Malik, I did this as a kid. I managed to invent modular arithmetic as a game; the big insight for me was that, although I had originally set ‘Z’ = 26, it was also true that ‘Z’ = 0. I suppose that it was doing these arithmetic problems (for fun) that allowed me to actually complete the memorisation.

After deciding that counting should begin with 0, I've tried to relearn them, but it didn't take (it's easier to just add or subtract 1).