The ones who can't are usually weeded out of the industry pretty quickly.
But of course, if you're not shooting a porn scene and you're having anal sex in the privacy of your own home, a shower or baby wipe is usually good enough.
It seems like some form or another of this question always pops up, and my answer is usually this: The best way to introduce a new concept is to watch a porno of said concept together.
Only then will real change come.
.
What Mozart was to music, Stephen Hawking was to black holes, and Mother Theresa was to helping people, I am to a good anal pounding.