I have also cleaned keyboards down to the contacts beginning with my C64. If don't desire to remove the key caps because you risk breaking the key posts, the process is tedious but takes only 30 minutes. The contacts are carbonized rubber and on the bottom of the key posts require just rubbing with a Q-tip and isopropyl alcohol. The flat part or as some people call it, the membrane cleans best with a rubber eraser followed by an alcohol wipe.
I only remove the key caps to Retr0Brite them, plus I have a supply of keys and key posts if one breaks. May The force be with you if you go that route!
