IMO most of those dressings do more harm than good when you consider the long term effects. If you're trading the car in 3 years then it doesn't matter, but on a 10 year old vehicle you can always tell the people who used plastic trim dressing every month when the car was new.
I'm sure the next three replies will be telling me how *this* product doesn't do that and I'm wrong. But I keep my vehicles for 10 years or more and I'll skip the crap that sucks the life out of the plastic trim.
Sounds like Plasti Dip would be an excellent option. I did the outer edge of my faux gas cap on the back of my car 2 years ago and it still looks good.