You need a decent torch (Sungun, Brinkman, powerful LED, natural bright sun even) or a halogen light to examine the finish, inspect the clearcoat for swirls and scratches and work to remove these and the contaminants bonded to the car, once you have these at an acceptable level and polished up nicely the wax is just a slight enhancement on this.
Grey / silver / white can look amazing when done properly - it's all in the initial prep, do it properly once, wash carefully so you don't add defects and then just keep topping up with a quality wax.
Help any metallic finish to "pop" and get the clear as smooth as you can to reflect like a mirror, worth the effort IMO even if it only makes a slight difference in the eyes of 99% of viewers.
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