I am an asshole expert and anal connoisseur of everything that can possibly be stuck up an asshole, whether its yours or mine.
When it comes to anal play, I recommend that my clients eat a balanced diet beforehand that includes a lot of probiotics and fiber. It's always good to have a healthy colon to play in. Also, don't eat anything SPICY! There's nothing worse than feeling the remnants of that that jalapeno burrito you ate two days ago.
Second, I recommend that my clients clean out their asshole with either an enema or a glycerin suppository. I myself prefer a glycerin suppository (it gives you an instant shit) with an enema flush afterwards. A wine enema makes a great finish after all of this. Having a clean asshole is integral to fun, clean experience.
Moving on, when it comes to prostate/ass play, I always use a latex gloves and/or finger condom with plenty of lube. While I'm giving you your yearly anal exam, I like to pull on the anal sphincter (that band around your asshole) as to get you 'loosened' for more fingers, a dildo, or my strap-on.
(Sorry for the long post, . . . I'm very passionate about this subject!)