Enema vs Suppository?
Both have their time and place.
But if you are preparing your sub for an anoscopy/proctoscopy, you should not use a large volume enema immediately beforehand. Any water remaining in the ascending and transverse colon will surely find its way out the moment you insert the anoscope/proctoscope and get up really close, ready to peer inside with your little torch/flashlight. And you may cop a face-full. I'm speaking from experience - I was the sub, and my GF was examining me.
Instead, try the best of both worlds, a mini glycerine enema (only 60cc, or 2oz) with the potential effect of over ten standard glycerine suppositories, already fully melted, going up your bum at once. It sounds horrible, but trust me, it is very relaxing and very thorough.
The mini enema can contain:-
1. 20cc of pure medical grade glycerine - BSP/USP grade,
2. 40cc of pure drinking water,
3. A pinch of salt to prevent the water being absorbed.
Squirt it up using a piston syringe with douche nozzle, or simply a small rubber bulb syringe.
Please remain seated after the main performance has ended, because there will be a short encore a few minutes later.
Ask your doctor/nurse/mistress/master to bring you a glass of wine (and a ciggy if you smoke), while you relax on the loo. And that's all there is to it. After that, your bum is totally empty and you are ready for any kind of play.
Brachio.