First of all, are we talking anal play on you, her, or both? This is important because, while the "breaking in" techniques are about the same, only men have a prostate, so the pleasuring techniques will differ somewhat.

Psychology also seems to have a more significant role in anal play than most other types of sex. Some people, male and female, have such an aversion to it that they aren't going to enjoy it no matter what you do.

My personal experience is that while one can usually help their partner overcome the initial feelings of fear, vulnerability and helplessness, for some it's just too intense and they'll simply never relax enough to get into it.

Can you provide more details?

BTW, for many that do get over the initial mental blocks, anal play can be one of the most physically and emotionally intense experiences for both the giver and receiver. Good times!