You'll have to finely polish the areas - but, it will be real tough to restore it to the condition of appearing new. I've used materials such as very fine steel wool to do work like that. However - I've found that you have to be really careful and not go too far around the scratch, otherwise, you'll have many other smaller scratches. When done, you could try a mild abrasive (tooth paste?) to polish off the area a bit more. Also, I've found that using a spray cleaner with a mild amount of amonia has done wonders to get the "gunk" off the faces of many of my receivers. The product I use is Dirtex. It is available at most places like Lowes and Home Depot.
Just try working on a very small area at first. Also, you might want to apply some blue painter's tape around the outside area of the scratch you are working on, so you don't go too far beyond the boundaries of the actual scratch. Best of luck to you.
