Try not to laugh. But when I get scratches on mine, I just take a black magic marker and, after wiping the scope area really clean and dry (of all oil that may be on to it) color the area with the magic marker. Then while the ink is still wet, I quickly blend it in with my dry finger rubbing in the direction of the scratch. Apply repeatedly until the scratch disappears. One application works for light scratches. Two or three for heavier scratches. No waiting time between coats. It dries very quickly.
Not all magic markers are the same. Some just don't work all that well for this. One brand that works very well on metal is Marks a Lot ... if you cannot find that brand, try to get one with the big fat barrel that, when marked on the address area of a magazine (for example), colors the type on that slick magazine surface such that the address underneath cannot be read. Then you'll know you have a good marker.
What is slick about this ... unlike touch-up paint, the marker doesn't leave a thick layer that is ugly and I was amazed at how close it matches the surrounding matt finish if you blend the ink while it is still wet using your dry finger as described above.
