I don't do this myself, but I know that when my boyfriend wants to have sex and my fiancée is in the mood but also on her period, they get in the bathtub. Their apartment has a fairly large one -- it used to be a handicap accessible tub and then it got moved up to their place -- so it's more possible there. Mess washes down the drain, they get dirty and clean, sometimes one of them brings a bath bomb into play.
Me? I'm okay with blowing my boyfriend if he really wants it, or fingering my fiancée (though, we've synced, so that's never really an issue).