Do NOT put any type of liquid on the wood, that will only cause swelling and more trouble than just a squeaking button. It might be any number of things causing the sound. Most of the time it ends up being the spring itself that's causing the sound. If it is the piece of wood, I would only suggest taking a pencil and trying to put some graphite in the grove the piece of wood sits in. I'm sure some others on the board will have some other suggestions to help you out.
I agree with John.
First try a little powered graphite.
Available at your locksmith's shop.
Actually, Sears used to sell it in the hardware dept.
(I do not know if they still do.)