I fist & double fist, but this is way advanced compared to using a dildo, or a real penis, so practice makes perfect. I recommend always cleaning out with an enema prior to playtime because it can get real messy. I always use puppy pads to keep the mess limited. If someone claims their clean never trust. Accidents happen & the last thing anyone wants when on tour is a shitty smelling hotel room. Having a plant based diet always helps. Lots of lube.

Im surprised a gorgeous creature into anal play hasn't been fisted yet. I do have tiny hands and am perfect for beginners if you ever want to pop that cherry (although it won't be a pop at all but a slow and sensual spreading of course).

As for preparation - you know your body and that is great. But I would never recommend that someone else just wing it. Here is a link to an incredible and thorough "how to" on cleaning out a rectum: https://howtocleanyourass.wordpress.com/