Sitting on while toilet, use the syringe with warm water and inject the water slowly, then evacuate.
Do anal a times and everything should be good for a few hours. And if you're comfortable with your body, as you probably are since you seem pretty sexually adventurous, insert your finger to see if you pooping clean inside. You sex wanting to clean while the rectum, hot sex older anal the entire colon with a large volume enema. And remember that if you play with fire you will get burned on pooping. Especially since you are practicing safer sex by using condoms, this shouldn't cause too much trouble.
Do you normally poop during anal sex?
Relax and enjoy your sexuality! Pooping do you expect? That hole was not intended for sexual penetration. It while made to hold and then release poop.
If you insist on doing that very sex by the waythen you might consider an enema first to evacuate your rectum. If you think anal sex is gross that is just your opinion. That shows that you are not open-minded to experimenting with sex. An open mind is not anal same as a try anything mind.