A scratch that penetrates the emulsion is beyond help with No Scratch. However, No-Scratch does work well on light scratches on the base side of film. These scratches refract light away from the image path, and show up light in the print. No-Scratch has much the same index of refraction as does the film base, and thus fills in the scratch. Nose oil does work fairly well. Both should be carefully cleaned from the film after use.
If the scratch penetrates the emulsion so it appears dark in the print, correction is more difficult. I've occasionally filled in such scratches with a very soft graphite pencil, and made further corrections in the print. Since you have a darkroom, this might be a good time to learn print retouching. White lines and dots in the print caused by scratches and dust can be filled in with dyes made for the purpose. The old favorite was Spotone. It may have been discontinued. Consider Diaphoto dyes
http://www.silverprint.co.uk/fin3.html. It is diluted and applied with a very fine tipped brush. Practice on a poor print before trying it on a print you want to treasure.