I'm also a male in my 50's, and was introduced into anal play in my early 20's, and have been totally addicted to it ever since. Thus the beginning interest in doing enemas.
Most likely after getting involved in some anal play that got a bit messy. Do remember someone I was seeing on an occasional basis, (with much more experience in such things than I was), driving with me to a local drug store to purchase a small squeeze bulb type enema.
And it was all uphill after that, eventually moving on up to a typical red rubber open top bag.
Now before any kind of anal activity, it's a total cleanout for me. Found that the small bulbs or even the Fleets only cleaned out the lower rectum area, and with the stimulation received, that tended to start my intestines doing what they're supposed to do, move things on down.
So basically for a 'quickie', a small bulb or Fleet would do, but for any extended or prolonged anal activity, a total cleanout is necessary for me.
Just wish it wouldn't take so damn long to do!
But I did discover that once done, and done completely, with nothing retaining up in there somewhere, I would stay clean for a good 10 to 12 hours.