All I have from experience, is that a good enema cleanout is needed for further fun.
Again. A speculum inserted up ones ass and bag nozzle attached, only causes the lower bowel portion to get get cleaned out. On the other hand, a good big enema prior to the speculum getting inserted, then a colon tube going up, gives a good sensual feeling, as your butt hole is spread wide open, with a long 14-18" tube going all the way up.
A preliminary E is needed, ( soapy or not ) if you want the recipient to get a FULL cleanout, if you want to get the colon tube all the way in without issues / pain.
After this, the anal speculum is an erotic TV show / video, as the water is pumped up her / his ass, with the speculum inserted and no ability to hold back the water, as their butt hole is gaping wide open.
No control of the recipients bowel movements with the speculum in, as the water free flows from the upper intestines, and a visual treat for the giver.