You can use any magnesium supplement or magnesium rich mineral water instead of epsom salt, but when it comes to getting things out from your bowel, then ENEMA/Colema or colonics should be the most appropriate replacement for Epsom Salt flush.
It is very important to wash your bowel after the cleanse, and the problem with prune juice is that when it causes diarrhea, it makes you sick, and makes you feel bad, while enema will make you feel GOOD!
You can also consider coffee enema, it will give you double cleanse!