If I can add a little here? This old RAAF radio tech can offer a tip, although basically for Australian readers.
While I respect WD-40, it does stay sticky, and dust that passes through a fan-cooled device will tend to stick in on corners, and build up.
There is in Oz a product by the name of ‘RE-ACT’, which advertises itself as a ‘radio/electronic corrosion treatment’, available from ‘selected’ radio-supplies outlets. It can be thought of as a lacquer, but it’s viscosity lies between WD-40 and lacquer. The old lacquer dries hard and with a slight yellow colour, and was the traditional insulation applied to fine bare copper wire. When a wire overheated due some problem, the then well-known ‘brown-smell’ was a warning of impending urgent problems, or that a fuse was about to blow. That smell was the lacquer melting, sometimes even burning. It was/is a nuisance when wanting to re-solder a connection, as it had to be scraped off the joint before the solder would bond.
RE-ACT, on the other hand, is easily applied with a paint brush, artist size & quality being best. With that tool you can avoid runs. Thin and nearly clear, it dries to an almost-hard finish that totally blocks moisture & oxygen from a protected device or board, is flexible without cracks developing in the finish way down the track. One device I applied RE-ACT to was/still is a 1999-2000 PowerBook ‘Pismo’. Two previous Pismos had stopped when the pins of some chips simply corroded away. The treated one is still fully functional, and often reverted to (with it’s wonderful 3:2 screen) when I want to get away from the ads, and just get some work done, esp. in Excel 8.
For non-Aussies (poor people) suggest you ask around professional electronic repair shops, if you have any left.