I’ve been doing them since August, with improvements along the way. I’d say:
Try doing one first, 250ml. Wait 2 days then do another with more, then continue upping it to 500ml.
If you’re going to do retention, do 2 rounds at 500ml cleansing first, with 1 tsp baking soda in 1L water. Or the lemon juice like you said, but go slowly.
Then you could do a retentive enema with the probiotics/nystatin (if ou can get it) at like 250ml or less. I do them no more than 3 times a week to give recovery.
Make sure you get rid of all the air bubbles in the tube. And don’t eat too close either side of doing an enema.
It took some time to train myself to not get a lot of flatulence shortly after, or the feeling of needing to go. What helped was laying on my shoulders upside down for 2-5 mins after, then on my right side. The flatulence I put down to my gut dysbiosis. I used to get it almost exactly at the 5 hour mark after doing it, but it is not as bad now.
But the main thing – go slow, don’t delve in to the lemon and probiotics. If it goes wrong, it’ll put you off doing more.