When I think of glycerin enemas, this is what comes to mind.
It would be a bad choice for the inexperienced receiver.
Someone more experienced, doing it INFREQUENTLY!! it may be a better choice.
I took an enema once that isn't something I would have wanted to repeat at the time, but now, maybe under the right circumstances.
Be careful! You want to do this on an empty stomach ONLY!
If you want a SINGLE enema that can really clean you out with one round This will work but use it SPARINGLY No more than a couple of times a year and make sure you are an experienced enema taker and are ready to be surprised.
Start the afternoon before, ideally right after lunch. Eat LESS for lunch than usual.
After lunch drink a 32oz bottle of either Powerade or Gatorade.
Rinse the bottle repeatedly till you can no longer smell the original contents.
Then put in 18oz of glycerin. After that's in pour in the contents of ONE Fleet enema or equivalent generic. Fill the Fleet bottle again with 4.5 oz of potable water. Add it to the mix.
Throw away the Fleet bottle.
Put the cap back on the Powerade bottle and shake it up good!
Then let it set overnight.
U S Room Temperature is fine. British room temperature might be on the cold side to get the best mix.
The next morning without eating anything since the previous afternoon, Drink some water, while you are prepping the bed or table for a Simms position enema place the bottle in a hot water bath in a sink or dishpan.
You should have 2 clean washcloths ready. One as a bite/twist rag the other to stuff in your rectum if you start to leak on the way to the toilet.
Once you are set up, pour the contents of that Powerade bottle into an open-top bag type syringe. Hang it about 3-ft above where your rectum will be when you are in position.
Get in the Simms position, and with the nozzle you are most familiar and comfortable with, take the enema as you would normally take a 2-qt enema. Be ready, it goes fast!
I pride myself on retaining 3-qt Epsom salt and soapsuds enemas 15 minutes.
I have done this sort of enema 2 or 3 times in my whole life, I have yet to get past 11 minutes!!
You won't need a second enema THIS gets EVERYTHING out!
Keep a dishpan or empty trashcan within easy reach of the toilet in case it DOES come out both ends at once!! If you fast at least 12 hours ideally more before starting. Odds are you wonāt, but the risk is not zero. It WILL feel like it's going to. If there IS anything in your stomach, it's almost certainly coming out, so be ready!!
Don't do anything physically strenuous for at least a couple of hours after. This will leave you feeling ragged for an hour or two!