What I always do after a flush is FIRST of all I drink a lot of water, like 3 liter, not at once, that'll give you a terrible stomach pain, because it is just too much, but divided over two hours. My experience is that you even flush more out... Then I prepare myself a mixture of Bentonite clay and psyllium fibre.
You dissolve the clay (l level tbs) in the water ( half liter), then add psyllium husk (heaping tbs) and stir, stir, stir, untill a gel-like substance is formed. Drink it. After that again: lots of water. The first bowel movement will be like the bowel cleansing pix on this site, at least for me it was... Since I do this all the time, now the clean clay-psyllium comes out in the form of my colon!!!
I think it's as good as a colonic, and way more cheaper! And it can't harm, as long as you drink plenty of water.