Yes to both questions.
I use the pinky (or "little finger" as I tend to call it, being British) count all the time to establish breaks, as a get-ready for a tilt, and as an aid to estimation. However, I will admit that a thumb count, although more visible and requiring more movement for some applications, can serve pretty much the same purpose if it's performed under misdirection. I think one of the benefits of practicing it is to strengthen and increase the sensitivity of the finger in question. This helps enormously if, for example, you want to pull down a certain number of cards from the bottom of the deck, or perform a one-hand bottom palm. I also think that passes can be made more invisible by getting the little finger more involved, rather than those spectators who are burning your hands being allowed to see that moment of tension of the fingers that are closer to them.
As for a source teaching it, do you really need one? If you understand what a pinky count is, then I don't think you'll get much from watching it on DVD or reading a description. I think this is an individual kind of thing, with the finer points depending on your own particular hand. I think basically, as with many moves, it's just something you need to play with until you can eliminate as much movement and muscle tension as possible.