I';ve tried and succeeded using a similar (more basic) product to the one Gally has posted. But be warned, this can go wrong if not treated with respect. You'll need a machine polisher and some glass polishing pads (look like DA MF pads, i.e. very thin). Modern Automotive glass has a thin layer of film inside the glass. If you heat the glass too much, the film will distort, leaving you with the only other alternative to this thread - syaing goodbye to £100 through your insurance for Autoglass to replace your windows.