I would start with a really good anal exam, feet up in stirrups and strapped, his legs spread, and his asshole at the end of the exam table, some good lube and several fingers, not to point of fisting (unless he wanted it or to try it), but a really good rectal exam and some prostate play and some sucking and ball playing!
I would arrange the lower strap so he could not slide back on the table as I went to work (I want his asshole well exposed), no pain or anything remotely like that, just pleasure.
I would also do several enemas with the bag on an IV stand, and set up so he could blast the results out of his asshole. I was also fuck him while blasting out the enemas. If he liked estiming, I would do a nice and pleasant estim session with a nice electro plug. Most males love this even if they don't know it. I would also use a spectrum on his asshole, and with mirrors and/or a camera on my PC so he could enjoy the fun too.
I've often fantasized about giving a male an enema on an exam table strapped in place. If he wanted it, I could do a three or four quart one safely and slowly and no more than he wanted. I would also do one at the same time with another nozzle up my ass with the bag on another IV stand while I gave him a good one. No pain, just pleasure!
I would also have mirrors all around the exam room so we could both easily watch the action. I would also jerk him off once or multiple times, also cuming myself. I would control when he came, because I would have his hands strapped behind his head.
I think I could make this last a couple of hours. My problem is I'm always so hot and horny I cum practically on demand and way too quickly, I am so sexually charged I don't have the discipline to hold back cuming.
I would also do a lot of nipple play with him.
If really close emotionally and both clean and healthy, I would be interested in doing a shared enema hose between us. I have always fantasized about taking someone else's enema up my ass and vice versa, back and forth. I just think that could be so hot, but they would have to be very close to me and very healthy like me.
I would have him on the examination table with a balloon nozzle in place and a large diameter hose to my asshole with a balloon, then with a three or four quart enema if possible, first one in awhile for him so I get a real load, and me then taking it up the ass and then giving it back to him time after time. I just find that so hot, feeling it coming from him directly, everything, up my asshole and body so I could feel his load up my ass as he pushed out his large enema, everything, I had just given to him back into my ass and then me pushing it back into him. Oh, ................... so hot! I can just feel him forcing it into me gently!
I could also do some nice soundings if he wanted! I could also help him empty his bladder with a safe catheterization!
I also would not mind switching places, me on the exam table and strapped up for action!
Bobby can't do this in reality for a number of reasons, but likes to fantasize about it.