You’ve already got answers about rice so I won’t comment on that.
Once you’ve noted the corroded places, clean it by using 99% isopropyl alcohol and an ESD brush. In lieu of an ESD brush, a regular toothbrush is usually fine but best practice is to adhere to ESD protocols.
The main area you won’t be able to get to is the BGA underneath some of the ICs. To clean under there, the board would need to be put through an ultrasonic cleaner.
I usually give any wet board 24 hours to dry with a fan circulating air over it, flipping the board around the 12 hour mark. Humidity is usually 30-60% where I live.
I tested this theory with half of my 12 tubs once, I did not notice any better flushes on either but it was a heck of a lot more work to cut compared to twist n’ pull.
With cutting, any piece of shroom that falls off in the tub and isn’t connected to the mycelia network will rot, risking contamination.