These dryer balls are awesome! Seriously!
I wasn't checking constantly; I just set the dryer for less time than usual, but a big load of diapers dried in 40 minutes less (at least) than usual AND the thick BumGenius AIOs that take FOREVER to dry were completely dry. Next time I'll try setting it for a little less time.
Here's some how to info that I found.
If you're making a bunch that is probably the way to go. I made 3 and they're about 3 inches across. I just felted them at my sink, it went pretty quick. I wrapped the wool into balls like shown in those links, put hot water and soap on them, and rubbed them in my hands, then did a second layer. With how well they work, I should make some more. I don't have any old pantyhose, because I wear them almost never, maybe I'll try a sock.