I always have a bath first and wash well. I don't use a douche or enema, I'd be in the bathroom for half a night, or morning.
We've never had a messy accident. Everyone's digestive system is different. I'm gonna be graphic, if you have sticky or loose poops, there it's probably more likely you'll have a little mess (and a douche may help with that) if you have "rabbit pellet" poops (which many people do have) there is less of a chance of messes. It has to do with what your body does with waste and how it processes it.
There have been days when I simply don't want anal, because I'm feeling like I haven't "gone" enough or I need to and it hasn't happened yet. We wait, then and do something else.
My Man doesn't allow anal on himself. One because he's the Dominant member of our couple and he does all the penetration and is not penetrated, two, because his digestive system works differently than mine and he doesn't feel comfortable with being touched there.