How is your BM before the flush? I found that I have to make sure to add a lot of extra bulk to my diet ( e.g Psyllium ) for at few days before the flush, or else I would end up with similar problems as you describe. This in spite of the fact that I have very regular BM's, about 2 to 3 times a day. One time the whole mess after the flush got stuck, enemas, prune juice, nothing helped until I went for a colonic. Now I try to schedule a colonic for the second or third day after a flush.
Hope you find your answer...