I never noticed the metal thing before...I'll have to check into it. I usually use a stainless steel measuring spoon and have never had a problem...but if you're concerned about it just use a plastic measuring spoon.
I prefer the whole husk psyllium (Yerba Prima) instead of the powdered (they're actually both a powder, but the powdered is a finer powder) because it doesn't set up quite as fast. The p&b shakes will begin to gel pretty fast so you have to drink them down right away. They both do the job equally as well, though.
Start with 1Tbsp Bentonite + 1 Tbsp whole husk (or 1 tsp powder) psyllium mixed with 8-10oz water or diluted juice and follow this with another 8-10oz glass of water. Gradually increase the number of daily doses as your body adjusts to the increased fiber. Some people require 3-5 daily doses to start seeing significant results...which may take a few days to several weeks.
You can use Bentonite without psyllium to absorb toxins, but if you want to eliminate mucoid plaque in the intestines you need to use it with psyllium.