[23479s882u]

I doubt whether water alone can thoroughly dislodge all traces for those of us with sticky, fairly solid poo.

Besides, there seem to be lots of cultures where people have water but not pressure, and it seems that they use fingers. (Often the left hand.)

I found kragen's answer above to be much more helpful, in that he explains both water-only and water-plus-fingers options.

I would feel a little uncomfortable about handling poo that closely and maybe getting it under my fingernails, but that's my own hangup. I don't believe my habits are objectively superior.