Answers to adhesive decal glues blues

Hi everybody, I was wondering what is the absolute best adhesive remover (from old decals) that is not goo gone, not mayonaise, not vinegar...etc. Today I used W-D 40 and it was ok just takes a while to see the results as it has to dry and evaporate. Any better suggestions? Thanks Bill

I am trying to master removing the glue that remains on fiberglass surfaces mostly. (for example fifth wheel Rv's)