To actually slow the gut Imodium or Lomotil are the go-to choices. I’ve used Lomotil since my surgery 16 years ago. I find it most effective to use it just at bedtime or before going to a bathroom-free zone (like a boat or bike ride). To bulk things up I use psyllium powder, also every day since my surgery.
I use VSL, too, but that’s awfully expensive (at least to get a useful dose) unless you turn out to need it. Some people (perhaps most) just don’t get pouchitis enough to warrant it. The VSL capsules are a fairly low dose, like most probiotic brands.