I've never seen any discussion on it either, so it must be rare. At 203k miles, my AT still shifts just fine and has never needed an adjustment. It can be done, though as a DIY job I'd speculate it is only for the boldest of us.
Regular drain-and-fills of the AT seem to resolve most shifting problems. In recent years, I've been doing it once a year while doing an engine oil change. Every other year I also add a bottle of Trans-X. Seems to help and doesn't cost a lot.
Beginning on the 4th page of the linked document (document page labeled 26), there is a section on adjustment if you'd like to know more.