This question came to me when i was watching a documentary about ancient rome with reenactments. And there was a scene set in a communal toilet, after they had done their buisness, they simply stood up and left. And i figure that cant be right, can it?
The tool was a sponge on the end of a stick.
The OCD says about Roman sanitation
The Latrines consisted of benches with holes over drains. Water for users' cleanliness was supplied in basins or channels.
Brlll's New Pauly says
After relieving oneself one used a sponge (Aristoph. Ran. 480-490, cf. Aristoph. Ach. 846; in Mart. 12,48 it is fastened to a staff and hung in the latrine, cf. Sen. Ep. 70,20) or a rag; using a stone or garlic (e.g. bowl, Boston, MFA, Inv. 08.31b, [4. pl. 11,2]; Aristoph. Plut. 816f.) was also possible.
Martial 12.48 illustrates the point:
Yet your dinner is a handsome one, I admit, most handsome, but to-morrow nothing of it will remain; nay, this very day, in fact this very moment, there is nothing of it but what a common sponge at the end of a mop-stick, or a famished dog, or any street convenience can take away.
This is, incidentally, what the Romans are supposed to have used to give vinegar to Christ during the Crucifixion. Posca was a mixture of vinegar and water that was basically Roman Gatorade. The sponge on the stick was the insult, not the offer of vinegar.
There's a new book by Ana Olga Koloski-Ostrow, The Archaeology of Sanitation in Roman Italy: Toilets, Sewers, and Water Systems that covers all of this. She points out (as did LegalAction in this thread) that the sponges were communal.