Agreeing with what's been said. Anal sex is painful without lube and preparation. How much preparation you need depends on your own preferences, and how you're feeling that day. For me, personally, I like to have a lot of foreplay and tp orgasm at least once before any anal penetration. It helps me relax and it makes the experience more enjoyable. Fingers first, before penises or toys, even if it's just one finger to work some lube inside.
As for orgasms... Never had an orgasm from anal stimulation only, but anal penetration makes other kinds of orgasms more powerful for me.