Contact printing with any liquid like Edwal will not work well, because, as pointed out before, it will interfer with the development, also it will likely leave a "halo", as the part of the neg with oil on it will have a ridge were the oil is not in contact with the paper. Try a sheet of diffusion material above the contact frame, say about 2-4 inches, this will be like a diffusion enlarger, instead of a condenser. If the scratches are not serious, this might work. I have used this technique in the past with some success, the only downside is that it will reduce sharpness unless the neg is in very close contact with the paper.
I have also used the Edwal oil and nose and ear grease, in enlargers, all with degrees of success, if the scratch is in the base, then there is a good chance that it can be hidden with one of these methods, if the emulsion itself is damaged, then some kind of retouching, be it digital or conventional is needed. I should add that this makes the neg a bit of a dust magnet, so it can increase the spoting that is needed, unless care is taken.
If I might add, without being chastised, this is were digital can really work wonders, as I am "Old School" and having done all this stuff with dyes, etc., its' so much better to be able to fix these in Ph---s--p!
Keith