Place a paper towel underneath each pickup to catch rust and keep it from falling into the guitar body.

Using an abrasive pad, carefully rub off the heavy surface buildup of rust.

Do not use a magnetic scrubber (steel wool), as the residue will be nearly impossible to completely remove from the poles.

You do not need to completely remove all rust from the pickups. The discolored look is a desirable feature, and many guitarists actually pay extra to have their pickups slightly "aged". Additionally, light rust has no effect on the performance of the pickups.

Clean off rust particles from around the poles with a cotton swab.