I can't answer your question, really, because I've only ever done the Master-Cleanse
with the b&p shakes. (yes, I got out 'ropes'! ooooh, exciting).
I hope someone else can answer your question!
If you feel like adding the b&p's - you can do that at any time and you can continue to take them after your fast too. (I did - and still got out mucoid plaque - even though the pieces got smaller and smaller and finer and finer)
Below is information on the b&p's...
Bentonite & Psyllium Drinks