That depends on whether you are giving or receiving the anal orgasm. I have never given anal orgasms by fucking a gape, but only when I'm in the process of easing the head inside them, so that when they orgasm, the head of my cock has only just pushed in.
It helps to really hunch over her when you're fucking her ass so that you get up nice and close to her - grip her hips a little and spank her. Get nasty with it.
It helps to have a big dick because you can place the woman's hand on your shaft and she can feel it protruding from her - I like to do that, just to say: "Yeah, that's right, that's how much is left".
