I am doing research on how many people wash their private parts after each pee and poop and find it hard to find materials on this.
Muslims are required by their religion to wash their private parts after each pee and poop. The Indians and Filipinos wash after each poop, not sure about after each pee though some say they do.
This aspect of hygiene seems to be neglected by most people and often you hear about skid marks and pee stains on underwear. Also spontaneous sex would seem less enjoyable will unclean and smelly bottoms.