Yes you are right. Linseed oil and denatured alcohol and applied as directed will smooth out the finish and remove the brown color of aged shellac. Stay away from the decals for the alcohol will silver them. It will take several times to make a smooth surface and then to same using shellac and linseed oil as directed will build up the finish. This is called French polishing. I recommend you practice on an old machine first to get the hang of this. Go slow but have fun.