Also 4 might insult people, and some conservatives may take issues with 18.

I agree it can feel weird, but first this isn't how we are used to doing it so it hard to compare, and also normally we want our fingers in very precise positions (probably because it's easier to show other people). When doing binary I feel it's easier to ignore precise positions. I just use the half of my finger after the middle knuckle and let my fingers move as they please. We only need to track up or down, so it doesn't need to be precise.

Practice helps. I'm not good at it, but I can manage it fine at this point. For sure it'd doable, but I rarely have to count, and when I do I can generally do it in my head fine. I could see myself using it maybe if tracking a large number over a long time, but I don't see that case ever coming up organically.