UKPassats

Hi all my black trim(loads of it) is looking a bit tired,its sort of black from a distance lol but when up close it looks like its got wax remnants and going a sort of grey. Ive tried the normal black to black,peanut butter,black wow,and g-techniq. All worked for a time but nothing seemed to last,unless I didn't clean the plastics thoughly enough.
Apart from spaying it black what products are you lot using,how did you prepare the plastics before using the products?
Any ideas. Cheers