In his book Post Exposures, Ctein oils in film for enlargements as standard practice. He uses Edwal No Scratch which is a transparent oil that has the same index of refraction as film and eliminates dust and scratches. He claims it is much quicker to oil and clean the negative then it is to spot each print.

From my own experiences I am in complete agreement. I do very big enlargements and small dust spots not visible on smaller prints become very noticeable on big stuff. It only takes about two drops of oil to coat the film. I clean the film after with PEC-12.

It will work with both color and b&w negatives and also helps minimize Newton rings.

B&H sells Edwal No Scratch, but cannot ship it because it is classified as hazardous material. Calumet sells it and ships it for about $10 a bottle plus shipping.