The Epsom Salt does a good job of getting the bowels cleaned out. (youle see what I mean)
Enemas or colonics are not necessary to do a good liver flush.

Its also a good idea to drink some apple juice during the days just prior to liver flushing. The maltic acid will soften Gallstones allowing them to roll out easier. Its not necessary, just an extra something for a better flush.

The Black-Walnut tincture is to kill parasites that may come out during flushing. Again, something extra but still not necessary for a good flush.

What makes for a good flush is getting the body to push out a good amount of bile.
The Epsom Salt opens up the ducts or openings where the bile pushes through.
The fats in the olive oil causes the body to dump large volumes of bile. This is dependent on not having fats in the diet for a time just prior to flushing.
And its dependent on having a good amount of bile there at the time of the flush. Which is why I wait a week after a cleanse for the bile to build up.