I have had excellent results with faded black plastic using Shine Supply Trim Coat Black.
On faded trim Trim Coat Black has a black dye in it and makes the exterior trim black again.
(Be sure to wear rubber gloves when using any chemicals)

After Trim Coat Black has dried (4-8 hours) I apply CQuartz Dlux Wheel & Trim Coating.
In many cases Dlux is fine but if it needs to be black again I use Trim Coat Black first.

CQuartz Dlux is my go-to product on trim. I darkens the trim and acts like a coating when dry.
I will state that IMHO it take 8-12 hours for CQuartz Dlux to dry. IMHO Dlux will lasts up to a year.
CQuartz Dlux is not a dressing it is a coating. When it's cured it's completely dry to the touch.

This is my 1-2 punch for making trim black and making it stay black.
Remember: Each product needs cure time before the next product application.






Notes: Dlux makes trim darker and has excellent longevity.
Trim Coat Black makes it black. Dlux seals the Trim Coat Black.

 

Ill tell you what not to use!
Trinova Plastic & Trim Restorer, I bought it on Amazon, it had great reviews however, It looks great when you first apply it but It only lasts about a week or until the first rain or washing.