really depends on how good a finish you want. are the scratches down to the colour or are they just in the lacquer? a good cut and polish might take a lot of them out but if it's beyond that then I would just take it to a body shop and get them to paint it. You'll save yourself a whole load of hassle and the finish will be far better than what you'll get out of a can. If you buy the materials yourself you'll save a bit of money too.