I’ve taken psyllium for about 19 years, since my surgeon recommended it at my hospital discharge. I’ve used powder, wafers, and capsules, and both flavored/sweetened powder as well as unflavored. The only form that didn’t do the job for me was the capsules. It doesn’t really slow the output, but it does bulk it up and make it thicker, which can be much easier to hold. To directly slow the bowel I use Lomotil, mainly at bedtime or if I’m going someplace without a reasonable bathroom.
I’ve found psyllium works well for me twice a day, with breakfast and dinner, prepared according to the package directions. For the past few years I’ve mixed sweetened Metamucil 50/50 with unflavored Konsyl, to balance the pros and cons of each.