I don't remember childhood enemas, may be there are no one than i was small.
At 11 was some prescription to do enema for some medical tests, but my mom didn't do it to me, use pills to flush colon.
I interested in procedure, self-administred from old orange bulb. Used 2-3 times at once.
Later, at 14-15 i bought hot water combination bottle from local store, 2000cc volume. And with some training it was easy to hold full capacity.
This year did my first colonoscopy, then get prepared use 2000cc enema bag (can hold up to 2.3L). After that buy 4000cc silicone enema bag, now can receive about 3000cc without difficulty. Will train to hold full bag.
For solution use only clean water, salt (10-20g/L) and glycerine (40g/L). Sometimes small amount of mineral oil (150cc from syringe with colon tube).
Than was young prefer high enema, than it flow very fast (1-2min full bag), but it hard to hold.
Now prefer use very slow flow, about 10-15min to fill and up to 15 min to hold. Much easier and more volume to hold. But first enema in series typically only 1500cc, probably because colon is full. 2nd and other 2000cc+.