On the motherboard, I would remove it, use canned air to blow it off well. Then ultrasonic it in a solution of distilled water and Branson cleaner.
Sorry I don’t remember how we used to clean the keyboards. But remember, it’s not the water that shoots keyboards out, it’s the contaminates in non-distilled water that allow it to become conductive. Personally I clean my keyboards with a Q-tip dipped in a pure alcohol.
I do remember washing older keyboards, but it been a while and if I remember, I’ll chime back in.