I just ran across this thread today.
I do not recommend using any lubricants that are not rated for electrical contacts. I know of someone who used WD-40 on an old, but expensive, mixer board resulting in destroying every pot and slider it came in contact with. WD-40 might solve the mechanical problem of the switch, but could potentially work its way into the electrical contact portion of the switch and create damage that may require replacing the switch. If this hasn't happened to you, you are lucky.
Di-electric grease might be a good candidate. Get advice from an electronics professional before lubricating your electronics with whatever is available in your household. Many lubricants have solvents in their formulas that are definitely dangerous to electronics.
Di-electric grease and tuner cleaner are two that are rated for electrical switches and connectors. There are probably others.