Removing glue residue

Race crew taped my race number on my ski with heavy duty duck tape. I cannot seem to clean off the glue residue. I've used warm water and soap, and when that did not work, rubbing alcohol, which did not work.  The square outline is obvious, less white, different texture.  Looks like a bad patch repair job. What do I use to get the new-ish epic ultra layup back to matching rest of boat?  I certainly do not want to mess up the gel coat.  Thanks

I use WD-40. Takes off the sticky goo great but leaves behind a slick sheen, which can then be removed easily with soapy water.
Acetone also works but is toxic as shiite and will really mess you up if it hits bare skin

One more for acetone.

I had glue residue on a paddle's carbon shaft and contacted Jantex to ask if it's OK to use acetone. Their answer was literally "Acetone is OK". Needless to say, it worked great.