"How do I get my girlfriend to have anal sex or use a toy anally?"
How do I get my girlfriend to have anal sex or use a toy anally? I'd also like her to play with my bottom but don't know how to suggest it.
Plenty of women enjoy anal sex - if - and it's a big if - it's done properly. What puts most of us of is having had the old 'Ooops, I got the wrong hole' trick pulled on us. 'Accidentally' and eagerly thrusting into an unlubricated, unprepared anus hurts. And it's put plenty of women off for life.
The second most likely thing to put us off is you asking for it, over and over and over again which (like the threesome request) only makes us more determined not to do it. A playful suggestion that you'd like to try it - along with a 'you don't have to if you don't want to, but I'd at least like to try stimulating you with my fingers', will get you much further.
I'd also suggest backing up your suggestion with some good articles on the topic, to allay any fears she has. Gently remind her just because something is seen as culturally 'taboo', doesn't mean it is. Not so long ago, it was 'unnatural' for women to work and only 'whores' gave men oral sex.
Things constantly move from 'bizarre' to mainstream once society attitudes relax or change. Anal sex is one of them. My book superhotsex has a good guide to first time anal sex.