The Adams Retouching machine indeed is a wonderful tool for those who know how to use them. I have been using one for more than 40 years, and I can guarantee it will be of little help in solving emulsion scratch problems.
The machine was designed to increase density with graphite or reduce density with a properly ground knife or abrading compound on portrait negatives. It was never intended to be a "cure all" as some today claim.
A scratch in the emulsion can be repaired with india ink and a 00 Rapidograph
pen. Over light table place the negative emulsion down. Carefully ink over the scratch (on the base side) When dry, print as normal and spot and blend the white area in the print with Spotone or other dye for such purposes.