Added the bentonite
I decided to go with 0.5 g/L, or 23 grams total for 46 liters. I mixed the Bentonite and 1 cup of water in a blender, over the span of about 6 hours. It became a thick slurry. I then used a syringe to inject the slurry into the carboys while stirring. They clouded up immediately, although later in the day they were already clearing.