The mesh looking inserts on the lower part of the bumper/ front spoiler? I use Griots spray on car wash (lubricant that adds gloss and some wax protection). I scrub it with a light touch horse hair brush. After that if you want..add a interior protectant wipe (I use griots) It's like a dressing that can also be used on tires...
1988 325i sedan (Cirrus Blue Metallic, Silver Grey Leather)
2011 128i convertible (Blue Water Metallic, Grey Leather)
2013 320i sedan Sapphire Black Metallic, Black/Black