Don't use 湿 for “Moisturizing”: A common mistake is to use 湿 to describe applying lotion. Saying “我的皮肤很湿” (wǒ de pífū hěn shī) means “My skin is wet (e.g., with water).” For the positive quality of well-hydrated skin or the act of moisturizing, you should use terms like
润 (rùn - moist, in a good way),
滋润 (zīrùn - to nourish and moisten), or
保湿 (bǎoshī - to retain moisture/moisturize).