How to Have Clean Anal Sex

Many girls that refrain from anal sex do so for two reasons: concerns over pain and hygiene.

Less Painful Sex

Anal sex is painful in the beginning, but it can be made less so by using a lot of lube. Lube should be applied both to the anal opening and to his cock (don't just apply lube on top, apply all the way down to the shaft). The obvious then applies: start very slowly, only inserting the tip of the cock. Guy doesn't move at first, so the girl can get used to the feeling (this can actually take up to a few minutes, so be patient as a guy).

A good starting position is spooning. Her on top gives her more control, but also more responsibility in making it "work", which is not suitable if she's never done it before. Doggy style may be too painful to start with.

Pain as a result of anal sex goes away with training: it will always be a little painful in the beginning, but the rest becomes much more enjoyable.

Hygienic Anal Sex

The only way to have perfectly clean anal sex is to use an enema. The enema is filled with hot water which is then sprayed into her ass. This makes her poop out everything (after repeating a couple of times). End with a shower and you need not worry much about getting shit on his cock.

Enemas can also be used for most advanced anal sex: ass licking / sticking tongue into anus ("rimming") and ass-to-mouth.