Firstly, this scratch appears to print - white. If the scratch is on the emulsion side, or if the emulsion is disrupted or removed, it will print black, and is more difficult to mask with Spotting.
With respect to your comments on your Spotting abilities, this print will be very easy to Spot effectively, and as such, is a great example on which to practice or learn.
Spotting is probably easier to show, than explain, but its major secret is implied in its name. Spotting is just that, take a very fine brush (number 00, and trim some more hairs out if necessary), and apply the paints in tiny dots to mimic the grain. Spread them apart to mimic the grain. How you spot a print, is governed by the print, or particular area of a print, in which the spotting will occur.
With this print, as I said above, take a very fine brush, and some B&W paints (I prefer the ones that come in a pallet or tray, like water colour paints, and I find saliva is the best medium for viscosity and wet-ability, or adherence to the print, especially RC prints - but I have used black ink from a pen, when nothing else was available.), and start applying the paint in very small dots randomly along the visible scratch. At this initial stage, just spread them randomly along the scratch, and practice creating very fine dots, or spots, and dont worry about trying to put them close together. When youve reached the end of the scratch, lean back and evaluate the print. Is the scratch less noticeable? Then repeat the process again placing new dots between the others, as needed. Sit back and evaluate it again, and repeat until you can no longer find the scratch when viewed from a distance. And remember one thing - it is usually easier to apply more dots - than it is to remove some, or reduce their size.
Every area of a B&W print, is just a darker, or lighter shade of grey. You can create every imaginable shade of grey by varying the density of (or how close together are) the dots. Same principles as inkjet, or offset printers, etc, and similar to grain. A few small dots, widely spaced, will appear as a light grey, and where more densely packed together, will appear darker, or black. Always evaluate it at a reasonable viewng distance.
Give it a try (or a couple of tries), and let us know how you went.
Brett.
