What is the religious ruling regarding the cover used by a person who has masturbated, and what must he do?

The default state of what a person covers themselves with is purity, unless one is certain that impurity has reached it. Semen is pure, and it is recommended to wash it when wet and rub it off when dry. As for pre-seminal fluid (madhy), it is impure, and the spot it touched must be washed.