I know this is of interest and has come up before. I have perfected it.
Use the 4 qt. Klystra bag.
Take a rubber colon tube slightly larger than the opening at bottom of bag.
Find the smallest fountain pump, around .1 amp with a discharge "spout" which will attach to the end of the colon tube. Insert tube snugly into bag so that the end of the tube attached to the pump is in the very bottom of bag.
Attach to other end of tube which is hanging from the bag any extra tubing to give you the desired length of enema tubing.
Attach the latex double ballon nozzle to end.
Presumably you know what to do with the above.
Also install in/on tubing a stop clamp and an inline back flow valve. (OHN has all this stuff) Or a higgenson pump which will serve the same purpose.
Hang bag by bed slightly lower than point of entry.
Plug in pump, which cord is coming out of top of bag, into an extension cord which goes as far away as possible to an electric timer set to the desireable enema wake up time. The reason for the distance is so you don't hear the click of the timer, which for a light sleeper would spoil the fun.
The latex retention nozzle is far more, in fact totally comfortable for falling asleep than the silicon. Been there, done that and they don't last. The comfort is key.
The amount of pressure is of a degree equal to a bag about 18 to 24 inches high. Be sure to confirm this youself by putting your finger against end of tube when pump is on. You should be able to easily stop the flow.
Actually the flow is a little slow, but persistant, for me so I actually have bag hanging at the lower than entry height from a stretch cord, which lifts the bag as it empties. You WILL wake up somewhere along the way.
I use 3 quarts, and am always wide awake at least halfway through.
I wrap a heating pad (optional) around the bag which heats it to a perfect 100 degrees. Of course that depends on the pad and setting etc. so experiment.