I'm a big believer in that if it hurts you're doing something wrong. Anal sex should NOT hurt if it does you might want to take more time with foreplay, use more lube, or just go slower.

That being said if you do regularly have pain while having anal then woman on top might not work the best for you since the anus has a tendency to tense up a bit while squating like is required for woman on top anal. We don't have any experience with the reverse cowgirl position but with her facing me it's no different really than woman on top vaginal sex. Other than it is a little more difficult to get in, but after that the only difference is the sensation.

Missionary anal would probably be more your cup of tea. Especially if you use a couple of pillows to raise your butt off the matress or floor. My wife really seems to enjoy anal this way since it doesn't seem to allow as deep of thrusts as doggy style. It's my personal favorite since I get to see her eyes while we do it and know that she is truly enjoying the experience. Which is a huge turn on to me.