For those who recommend using Pledge on the fingerboard, do you need to......

Many people posted just to spray pledge on a cloth and wipe on fingerboard. Do you do this over the strings??? I would think it would be bad for the strings and hard to get underneath them. So am I correct in assuming (even though it wasn't stated) that you must take strings off first?

Also..I live in the desert of Arizona. Dryness kills wood here. Anyone have suggestions on in-the-case humidifiers??? Thanks