Standard WD-40 is a great lubricant for certain items, good for getting rusted bolts unstuck, but not the same as electronic cleaner, which leaves no film and does not conduct electricity after drying. Most electronic contact cleaners have a fast drying agent, often denatured alcohol, which leaves little of no film, while it dissolves corrosives and carbon. Keep in mind, though, it is a solvent, which can react with many plastics, and dissolve the inside of switch contacts when sprayed heavily.
Now, most of the switches in our keyboards are carbon contact switches, which also includes key-strips. They can be cleaned with denatured alcohol and a Q-tip, then allowed to dry, which takes just a few seconds and you are ready to go again. Some, however, cannot be cleaned because they are hermetically sealed to prevent moisture intrusion.
Why manufacturers of arranger keyboards went to these switches was they were cheap - follow the money, honey! Back in the old days, positive, latch-switches rarely failed, and when they did, they were easily replaced. But, we're stuck with what we have.
As for just pulling out the plug, make sure you have the volume turned all the way down to prevent surge problems in the main amplifier of the keyboard.
Hope this helps,
Gary