Is it sufficient to rub an impure hand under water, as in ablution, or is it necessary to wash each finger separately?

"Waswasah" (whispering of Satan/obsessive thoughts) is an illness that must be combated by ignoring it. As for washing a hand contaminated with urine, it is done by pouring water over the site of the impurity and allowing it to flow, and one wash is sufficient. However, tangible impurities must be washed until their substance is removed, unless they are minor and excused.