I only had a couple of enemas when I was a youngster. First time I remember being held down and Mom working the nozzle into me as I cried and resisted. Have no clue as to the quantity. 2nd one I had some sort of bowel problem and was sitting in the tub with the nozzle inside me. Again, no idea how much. By the time I was 14 or 15 I'd self administer when the folks were away, always whatever the bag would hold, several times.
My first girlfriend got hers from her Mom, sitting on the toilet (she told me, lots of soap, lots of water, lots of crying and begging. She didn't know how much, only that it was too much. We did some anal sex (early form of birth control), and I suggested that I give her enemas prior. She flatly refused, saying that every memory of enemas was bad--burning from the soap, feeling like she was going to explode, etc.
One evening we were going on a date, and she met me at the doror, and said, "looks like you're going to get your wish." I had no idea what she meant but then she said "Old Geflushinus!" I still didn't get it (DENSE 16 year old), so she finally said, "What you wanted to do to me!" Finally it registered. So we planned for that evening (she was in a fair amount of constipated distress), and went to her house while her parents had their bowling nite. I filled her Mom's open top bag, stuck the rectal nozzle on, told her to get "bottoms up," lubed up the enema nozzle, stuck it into her, and started to fill her. She wasn't wiling to take much (afraid of the water), but it got things started and she was able to "go." After that I gave her quite few enemas, in the process getting completely hooked on giving; I used to give them to her at the beginning of her periods. They helped a lot with her cramps and kept her from getting constipated when she was iin her period. I DID give her one full bag enema. I proposed an enema to her after sex one day, and as we started, I told her, "this is going to be different." You have to take the entire bag." I was already pretty Dom, and she a natural sub, so she agreed, with some quiet complaint. I put her on her back naked with her knees drawn up to her chest, lubed her up with vaseline, and slid the douche nozzle into her. The water flowed right into her with only a little complaining, she got right up and emptied--which was when learned that I loved the sound of water and feces pouring out--the splashing and groaning as she expelled. I don't have a scat fetish, but I want to hear results. I' ve stayed in the bathroom with my enema partners while they expel ever since. Her comment was, after she was empty and had rinsed herself off..."I guess if you know it's all going in no matter what, it all goes in..." The comment was about the fact that she'd resisted "taking the full bag" from me for so long in the belief that it was too much, but the truth was that it went right in. I have remembered that comment from that day till now, and I almost always do give a full two quarts, even to inexperienced receivers. I may do a prep enema of half a bag, but most of the time I give a full bag, followed by another to make certain she's clean. An enema is cathartic in more ways than one--it cleanses the body, re-establishes the proper pecking order, and adjusts the atttitude. I also love to receive (still Dom when I do, no matter the publicity), but that's another story...