never fancied sticking something up there myself but whenever i go for a colonic (which is fairly frequently) i always get the lady to do a coffee enema afterward.
it does seems to stimulate things a bit, namely my appetite, but nothing really significant. would probably need to be doing it more frequently.
however, the flushes seem to be far more dramatic and the coke flush really moves a lot more about than the other styles of liver flush.
another thing i've found good for stimulating the liver/gallbladder is drinking chanca piedra tea. a couple of glasses of that back to back can be really good.