http://www.ebay.co.uk/itm/Polishing-Foam-Sponge-Cone-Metal-Pad-Car-Wheel-Hub-Care-Polish-Buffing-130mm-/151993769733?hash=item236388df05:g:w4QAAOSw~OVWzW0A
You need one of these!
Once polished, it's a good idea to seal the exhaust tips with a heat-resistant sealant or wax to help keep them clean.
