(photo by Gary; nail "pruning shears" shown for scale)
This here is a useful tool.
As I've aged, my toenails are those of the typical Ultrarunner--beat up (see photo here). One of the biggest problems is the thickening of nails, particularly on my second toes. They are so thick that trying to cut them is pretty difficult.
Enter the Dremel Tool--a mini-grinder with multiple attachments for hobbyists and do-it-your-selfers. A few seconds of grinding and I can perfectly reduce and shape the nail to manageable proportions.
I have no financial interest. It's available at Lowe's.