The water will evaporate, after using soap, rinse thoroughly with boiled water or de-ionized water, it will not harm the switches, just dry with a hair dryer. I have done this many times without a problem damaging components. Don't saturate the board or immerse it in a tank, just scrub the contaminated areas carefully with a stiff toothbrush.
The original manufacturer probably used water-soluble flux and cleaned the circuit the same way using de-ionized water.
If the switches are not contaminated, then don't put any soap or water on them.