I'm not an enema lover perse, but I give myself 4 - 2qt water enemas before sex, to be cleaned out. Sex in my case means xxxl anal toys, stretching and colon deep play.
Only yesterday I had a good looking guy butt fuck me (since 5 years I had some cock again, but that's another story) and some clean water was coming out, but he knew I didn't fully expelled anything.
I have had a few occasions that some water did not expell until the next day.
My way of taking an enema is simple. I first empty my bowel, than step on the scale to have an idea of my empty weight. Than I fill a bag with normal warm running water from the shower, not to hot, but warm.
Than I insert the enema, sometimes I can not get the whole 2qt in and expell and try again.
I almost always end up doing 4 bags of 2qt until absolutely clear water comes out.
In between the cycles I step on my scale to measure my weight so I can guestimate if there is still some water in me, before adding another bag.
And 2qt usually comes out in 3 to 4 flushes, the last ones not until I walk around in my room.
And sometimes it doesn't come out at all (the last bit of water), and than I lay on bed with two towels and pump some toys in and out to kind of suck the water out that way.
Eventually I'm clean. Oh, it takes about 1 hour total.