Removing decals safely

Hi,
I’ve just bought a couple of N scale covered hoppers (1 Walthers PS2 lettered for Santa Fe and a Con-Cor 3-bay car lettered for Tabor Grain) and I would lke to backdate the cars by removing their consolidated stencils. How can I SAFELY remove them without damaging the paint?

These are not decals, but are printed on the side of the car in a special ink. Over the years, I have mastered the technique of removing car numbers and consolidated stencils by VERY carefully scraping them off with a razor blade or modelers knife. Walthers Solvaset can be used, but it is difficult to use this on a very small area like N scale consolidated stencils or a single car number.