I did a liverflush when I thought I was parasite free. I felt tons better after the flush, and the flush itself was not painful or anything. I did find out after I did the flush that I still had parasites (fecal test). My naturopath told me it was OK to continue to do the flushes, but to also continue with my remedy for parasites. They recommend to be parasite free before you do a flush, because the parasites can block the flush and you might have a harder time.
I hope this helps.