I have tried all kinds of soaps. All the ones listed. Kirks, J&J Baby shampoo and body wash, gentle and nice, regular body wash for adults, Netrugena, which I felt was way too strong for me, Ivory bar soap, cut up and made into a liquid, I like Ivory dish soap, while it doesn't have any harsh stuff in it, Dr. Bohnners, Peperment, which is really nice.
All in all, I usually get 2 quarts of soapy water in me, then open the other bag and let the non-soapy water flow behind the soapy water. I refill both bags, usually there is some soap left in the first bag, I empty that one first, then the second bag. Usually I get 3 quarts in me each time. I keep doing the same thing, the soap goes away and then I wait till I empty out and I start over with either some baking soda and some salt.
I only use soap if I want to spend a few hours giving myself an enema. I enjoy the feel of the peperment soap the best.
Some like harsh soaps, I enjoy the mild ones.
When I use Dr. Bohonners, I usually squirt it in till the water turns milky. That way I get a second filling with some of the soap that is left the first time.
I have two 2 quart open top bags Y ed together.
I don't think I ever measured how much, I just pour it in.