They do make trim solvent. It is a little tricky to work with. To much solvent and the color (which is in the glue) will be gone. Not enough and you wont get a good a stick. Also there is no repositioning like with the windex method. I do keep trim solvent around. I like to use it to clean a plane after covering. The dark colors always bleed onto the light colors. The trim solvent will clean it right off.
I also found it cleans the adhesive left behind from ARF stickers.

David