Don't be afraid to try the "Cleaning and Repair Shellac Finish"! It took me months to get up the nerve to try it on a Pfaff 30 that my rag must have had some chemicals on and I messed up the finish on. A board member encouraged me to try it and now I see why. I have not completed the shellac process yet but the denatured alcohol and linseed oil made that machine look like new! It just took a little time to get it done and one of my husband's tee shirts. I should have taken before pictures because those of us that have not done it before would believe the difference, it is rewarding once you get it going. I fully expected it to be gray again the next day but to my surprise it still looked great! So go for it and good luck!
Lisa