God damn it, anal plugs.

They get anal plugs, but really big ones to make sure no one leaks.

Oh, it stretched their asses, made them bleed a bit, but it's better than shit getting all over the place. Their blood made good lubricant anyways. And they didn't fall out as the girls kicked and gasped, their mouths open in silent fearful and painful screams.

They make the girls who are next wash them when they are done.