For the sake of simplicity and convenience, I will use "bottom" to refer to the penetratee and "top" as the penetrator. Just a few things no buttsex session should go without: Proper posture while pooping is also important. Being gay is so much fun. The easiest place to do the cleansing is in the bathroom. And sure as hell don't bop it.
To avoid santorum the unpleasant mixture of nasty fluids caused by buttstuffyou need to get good and clean, so here's a coherent list of things you should do:
How to Avoid a Shitty Time: A Guide to Buttsex
It's silly I even need to mention a thing like consent, but those dicks amongst assholes ruin a good time for all of us. It doesn't matter if it's large or small, just that you have it, preferably attached in the proper area. They can also be used if the bottom opted not to use an anal douche to make sure everything's clean up there. So if you object to the usage of an anal douche, poop an hour or so beforehand and hope your fibre-rich diet cleaned everything out for you. Personally, I prefer a handheld one. Planning it out, in my mind, is the most tedious part of the whole buttsex process, because it makes me super anxious and that's no fun. You can use a douche over the toilet or in the shower, just so long as there's a drain nearby.