I piss on the hands to sterilize them before shitting and wiping my anus with my bare hands, because the paper is likely to have shit residue on it from the person before.
Then if my hands get a little dry from wiping I cum on them as a moisturizer, and sometimes I have to blow my nose over them too if I cum to little. Now my hands are nice and smooth without strangers germs.
Then I go out and finish my set.