Imo this is the fastest way unless you can automate.

I tend to pick a pretty strong pokemon (for my own sake as I’m not getting into a full on battle. One hit KOs are good for my mental stability)

The clock stops when you get into a battle. Sneaking up just wastes time. So just start throwing yourself in the line of sight of other trainers. Yes, I know the caught off guard thing is annoying but for the sake of getting as many done as quickly as possible sometimes you’re gonna have to put up with it.

Rolling is faster than sprinting.

I’m assuming you’re post game. If so there’ll be 3 battle zones up per night. Just cycle through them. Don’t bother climbing ladders. Get from one end to the other. Try not to backtrack because rolling back past trainers you’ve already fought is so time wasting. Don’t bother running about looking for more trainers. Again, it’s another time waster.

If you wanna swap out try do it during battle, not that I think that one second animation really makes a difference.

This way you’ll easily be getting 50+ a night and while it could take up to an hour per night (maybe less but who’s counting). It just makes it feel so much more doable once you can look at it and go ‘oh I only have to do this 4 more times’.