You poop the stones... They say that everyone has gall stones and that passing chaff is important as well (which a Liver-Flush also accomplishes). Personally, I recommend doing a parasite cleanse during the Master-Cleanse and then a Liver-Flush at the end. But adding the parasite cleanse is my own invention and is NOT according to the book's protocol.
It is best to do the cleanse a MINIMUM of 10 days. Your metabolism will return to normal once you begin eating. Exercise is the very best way to up ones metabolism but it takes awhile of doing it faithfully. I was able to maintain my normal exercise regimen while fasting. I think this is best since many toxins are cleansed through the skin as well.
Being tired while cleansing is normal since the body is doing a lot of internal detox work (plus the metabolism does slow down - I was cold everyday after day 6 or so). Give yourself time to rest - read a good book or sit and watch a sunset. I took a nap almost everyday of my 21-day cleanse. Paid for it with crabbiness if I didn't. ;^)
I can't tell you about P&B since I don't do that. I did an herbal Colon Cleanse from Dr. Natura about 10 months ago and saw some rope at the end of that.