MODELSTRIP. It is for models. A paste you brush over the model or parts you want to shift. Seal the model in a plastic bag and place in warm place for 10 hours. Excellent to remove paint and decals. HOWEVER. It's a UK product (may be available in US).
Note.: It says it MAY NOT remove some cellulose,polyurethane and factory finishes. I am about to try it on a G Scale Porter (LGB) Casey. Here's hoping it removes the paint/ink decals (as that is what most are these days (INK!).
Some recommend brake fluid. Huh! Plastics are all sorts these days. Brake fluid good for one..death to another!! ISOPROPYL ALCHOHOL and ACETONE did not work on LGB body. Acetone slightly melted the plastic until washed in water..it also smeared the printed lettering all over the place! Eventually got the job done with fine wet and dry and a small screwdriver "scraper". About to try the paste on Loco #2
So beware.