Do you tape the plastic when detailing? Most of synthetic waxes do not leave residue or discoloration.
I still can't get rid of the white stuff on the mud guards, since the day they sold it to me.
when use #26 wax i almost always goof up and get some wax on a trim piece. Mothers back to black cleans it right up, give it a shot.
You just wipe it on, wait a few seconds then buff it a little with a rag.