Older adhesives are dissolved in a mixture resembling paint thinner. The newest adhesives do not depend on the evaporation of a solvent and can be hard to remove.

I would start with the paint thinner, then 3M adhisive remover, D-Limone (pure concentrated orange cleaner) opps, goo-off, "Latex paint remover", 3m 5200 remover and finally chill it and scrape it off.