I just wipe on black magic plastic and vinyl protector pretty heavy with an old sock. The white [censored] is gone, and the plastic looks great. It is worth putting it on even if you don't have white wax on the black plastic.
I think Back2Black will only temporary mask the issue. You'll need to remove the residue first -- by either method mentioned above (mild APC, pink eraser, PB, etc), and then apply your dressing.
Or use something like bondo restore black. It's a black pigmented liquid that actually makes black trim black again. Lasts a long time too. I know I have a bottle of it out in the garage somewhere.