Here's a suggestion I got from this forum: treat you plastic/vinyl trim FIRST with some trim protectant before applying the wax/sealant/coating LSP of choice.
Some detailers do this before compounding and polishing, BUT it does make using painter's tape less likely to adhere to the trim, for those who protect the trim this way.
That said, I sure there are many fellow Autopian detailers, both professional and do-it-your-selfer's who have seen and removed wax build-up in emblems or the white residue in exterior plastic/vinyl trim or panels. I've resorted to Q-tips soaked in PPG's No. DX-440 wax remover (pre VOC-compliant), old tooth brushes soaked in Optimum's Power Clean, and even round toothpicks to dig out old and encrusted wax build-up in emblems.
I often wondered why non -OCD people "allow" this staining and residue build-up to occur on trim and emblems, because, quite frankly, it looks terrible and unsightly/unprofessional, to be politically correct and polite. But then, I've answered my own question; they just don't know or care: they are not OCD individuals nor are they true detailing professionals.