As I have mentioned in the past, periodic application on unpainted black plastic with Turtle Wax ICE wax works well. It doesn't turn the plastic white after application, either. (You can use it on the rest of the car, too.)
There4 are lots of products that address the cladding -- the best I've used is a newer product -- Blackfire Tire & Trim Sealant. It has made the cladding on my wife's 2014 look new and it has lasted for weeks thru several rainy days and a major snowstorm.
To apply, I washed normally and then an all-purpose cleaner before applying.