When fasting, you really SHOULD be cleaning your colon out. How else do you expect to get rid of all those toxins? Many people neglect this - and then wonder why they get SICK while fasting. It is because those toxins are literally - just sitting there! Of course you will feel sick!
I have discovered that magnesium is the best way to clean the colon. It does not lead to cramps, like sena products. It is very cleansing, and will help with the "smell" (people fasting tend to have a stong Body Odor due to toxin release). I like to use a product called "CALM". Type it in on the internet - you sould find some good sources to purchase it from. Adding a psyllium/benonite drink (as you have suggested) will also be beneficial. I sometimes avoid this - as it leaves me feeling quite bloated until the toxins pass. But - on the bright side, it will help the hunger pains!