ABSOLUTELY, if you have a sluggish bowel do not do the B&P shakes. Most people do not even realize that unless they are having a minimum of one bowel movement per day that The Master Cleanse is contraindicated. I think since you have done the Master-Cleanse before you will not have an issue with this but certainly the B&P shakes are not something you will want to play around with.
I wish you well on your cleanse. How long do you plan to go this time??
If you already bought the liquid bentonite, you can still use it in your foot baths and also I have taken to putting a small amount in water and rinsing my mouth with it after oil-pulling or just brushing and tongue-scraping. It absorbs toxins and makes your mouth really feel good!