PC boards are regularly cleaned in mnaufacture by rinsing with water. However, that's when non-waterproof components haven't been put on the board yet. Those might be connectors, and large pots. Perhaps switches, too.

Air, of course, can clean, but compressed air can also drive abrasive dirt particles deep into components that slide on one another, or drive conductive conducting organic particles between conductors that are energized when the circuit is working.

Trying to use wet components is always iffy.

edit: I suddenly remember that WD-40 is not a lubricant. Its name signifies that it's the fortieth formulation tried when attempting to create a solution that will drive water out of underground spaces from which petroleum had been removed. It's Water Displacement (solution) 40.

This also explains why its use as a lubricant is so short-lived. It isn't a lubricant.

WD-40 might help quite a bit, but in quantities beyond what we've ever tried to buy before.