I use Tamiya Panel Line Wash - usually black.
Here, over Alclad II for the wheels:
Here, over the kit's wheels; which were more of a "satin" if I recall correctly:
Over the kit's chrome grill here, followed by some more dirt and handling:
And applied too heavily here:
Oh, and also for the grill and wheels here - over the kit chrome:
and a blurry shot of the kit chrome grill with Tamiya panel wash: