For me that would have been the "Great White" open-topped bag I bought online when I was 16.
When it arrived, I was in a hurry actually to try it!!
I quickly realized I was going to have to do basically a cleanout enema at first before I was going to have much success.
I actually dug out one of my Mom's old 2-imperial quart bags from the stuff she had left behind.
Waited several days till I got a chance to do it right, but then I did a full cleanout. the difference being that I was using a bag that held 2 Imperial Quarts instead of 2 US Quarts.
Once I was at a clear return, I hooked up the 5-inch "barium" type nozzle which was little more than a 1930s douche nozzle with the tip cut off.
Made sure to fill the bag with a thick soap water solution, with the clumps broken up.
Hung it fro the ceiling over the bed, planning to use the knee-chest position. By the time I got into position something inside had already told me it was going to hurt, and I thought I could deal wit the hurt easier in Simms than in Knee-chest. I ended up using Simms.
I put some generic KY Jelly on the tip, and told myself, "You know where it needs to go, just get it there." I slowly inserted it making sure to keep it pointed at my navel.
Got it all the way in!!
I waited like 7 or 8 minutes with it in me just getting over my anxieties about the size. Finally I just decided that if I was ever going to do this it was time to buck up and go!! So, I took several deep breaths, cracked the valve, breathed out, and tried to relax. Within a few seconds my breathing was elevated, and within a few more there was that pain in my abdomen. I was OK, but maybe just because there was no one around I did cry just a little. Surprisingly soon I heard that sucking sound. At first I wondered what it was, because I had not used an open-topped bag for an enema before. Then I realized, I had heard it before! At the end of a douche. it was the bag EMPTYING!!
I realized that, at only 16 I HAD JUST TAKEN A 4-QT ENEMA ON THE FIRST TRY!!! The Euphoria of success was tempered by the pain, and by then some nausea, which I had not learned to anticipate in that situation. I knew touching the lower abdomen during a large enema is a no-no but I could not resist!! I could feel my whole large intestine, and is was HARD AS ROCK!! The valve was still open so I left the nozzle in, and headed for the bathroom. Somehow I had figured out from somewhere to put the bag in the bathtub with the open end pointing right at the drain. I stood straight up, and let it finish flowing. When it did I pulled the nozzle out and sat on the toilet, letting it flow!!
It all happened surprisingly fast. I would say it was in me no more than 6 or maybe 7 minutes.