I would say with your tongue. Be sure that the pin is turned on so you have plenty of light to see what you are doing.
On a serious note, I've just used some twisted steel wool (similar to how you would form a tissue to stuff into your nostril to stop a nosebleed). Make sure the pin is turned off, insert the steel wool fully, then give it several twists to rub off any rust or other gunk from the contacts.