Not sure if there`s anything different about it compared to the McKee`s, but Griot`s sells a Dried-on Wax Remover product too.
I once had a BMW with trim that had white stains. I figured it was just wax, but no matter *what* I tried, nothing would get it off. Nothing. Well, other than abrading it so much that the texture was altered; the [whatever-it-was] had penetrated/permeated down into the trim material. Some products would mask it for a while, but it was still there and would always reappear eventually. I finally just replaced the trim.
Re the time-honored Peanut Butter Approach:
-Doesn`t peanut butter do its thing by leaving peanut oil the surface? I mean...if I get peanut butter on something I wash it off, so I`ve never understood deliberately putting it on something (i.e., a vehicle) that I keep just as clean as anything else.
-If you use the peanut butter, and then wash it off, isn`t the stain still there?