Here's a cazy idea that came to me this afternoon though: How about placing your washed PCB in a vacuum chamber to lower the boiling point of the water - could that encorage it to dry out of all the crevises without excessive heat?
Yes, that is a good idea.
I dare say too much vacuum would cause all your electrolytics to explode though...
Maybe not.
Many years ago, I saw a circuit board mounted in a diecast box.
The idea was that this was to be used deep underwater, but it had to be quick and dirty and cheap.
To overcome the problems of water pressure which would have got in through the lid seal on the box or even crushed the box, the box was connected to an air supply via a divers breathing valve.
The diver breathing valve tracked the water pressure and gave air at very slightly above water pressure, and so the air pressure in the box kept out the water and prevented crushing.
The only problem was, what about the electronic components? Could they stand the pressure?
Phone calls to various manufacturers were no help, they said that their components could happily withstand very low pressure, as in up high in an aircraft, but no one had ever tested for high pressure deep underwater.
So, the circuit was built and tested in our departments pressure test tank.
The only thing that failed was an electrolytic capacitor which crushed under the pressure.
That capacitor was replaced with something a bit more robust, and the thing worked like a charm.
JimB