Wax off plastic?

[Groucho]

Hi all. I'm new here. I have a 2012 GTX with suspension...(not that that matters for my question). I was a little careless with the wax last year, and got some on the plastic front splash shield. I have tried a few different solvents and they appear to work but after it dries it comes back.
Anyone have a solution? (see what I did there?)

 

[Groucho]

After trying almost everything..turns out WD-40 seems to erase the wax.
Soon it will be time to put her in the water....can't come soon enough this year.

 

[Groucho]

Well...The white mark up's reappeared next morning...
Any other idea's??.