I've used it my old explorer sport. The mirrors and black plastic on the doors and rear pillar were just faded to basically white/light grey. The key with forever black is the prep, must be totally clean (I believe they either provide a cleaner or tell you to use alcohol - it was many years ago). If you follow their directions, you get a very nice looking finish, basically the way it looked when it was new. I believe I gave min 2 coats to get the sheen that I wanted and to cover minor streaks. Depending on the area you do, you may want to give more or less coats. I would bank on at least 2 though for an even finish. Just becareful not to get any where you don't want it!
I found it help up very well for a couple of years and then I sold the truck! If I had to do it all over, I would still use the forever black!
Hope that helps!