A washable and reusable cloth, while disgusting, is the most durable and environmentally safe.
And the most effective too, in my opinion.
To get really clean, I think some moisture is required. Unfortunately, TP usually shreds if you try to moisten it.
To avoid later irritation, I would need to pack pre-moistened wipes, or a cloth I could moisten, or perhaps employ a "spray bottle and left hand" technique.