Just wanted to be clear that what I wrote above was related to doing the BPs while fasting. They work fine when eating regular, though they take a lot of planning and dedication to do them correctly. They also need to be done for 3 to 4 weeks to be effective. I have tried them and 1st I don't have the dedication and patience required and second I hated the bloated feeling they gave me. Other folks swear by them.
I and many others opt for the oxygen based colon cleansers like OxyPowder which only take a week and do a bang up job melting the plaque stuck to your colon without the bloating. Doing colon cleansing after a fast is great cause the cleanse softens things up. Many folks do a colon cleanse as a matter of routine after a fast as a "Mop Up"
If you are still hell bent on the PBs post fast the link below gives you all the info you need to do them correctly.