Yes. The what was not dulled is creating the shadow. I'm quoting $400 more to replace it with a new board because it going to be a pain in the ass to install it.Til you go to all the trouble of trying to bring an old sign back to life, then painting/buffing it it's gonna cost about the same as a new panel. Are you sure the ghosting you're seeing is the old vinyl or where the sun hit it and hasn't dulled as fast as the exposed portions ??
What is polish compound?We go over it with some polish compound, and wax after it's lettered. Any more work that it's not worth it.