I was introduced to this, by a maintenance engineer at work, basically a pencil with a fibre glass head, that you can use to rub electrical connections in situ to clean away tarnish etc to make a better connection. I was removing old wiring in the engine bay and a solid core copper conductor came off the voltage regulator, it was easy to clean the spade terminal without having to remove the regulator and then replace the dodgy wire. just Incase it comes in handy for anyone else, only a fiver. Cheers Tony
I use one for cleaning IDC connectors on old computers/peripherals/cartridges etc. Works a treat. I use a contact cleaner spray afterwards because the pencil generates a lot of dust you don't want to leave lying there.
Wear gloves using them, you can get can be nasty splinters from the fibreglass bits that wear off. You can get steel tips as well good for rust spots.