I know there have been a gazillion threads regarding restoring luster to black plastic trim ... peanut butter, pencil erasers, Back-to-Black, silicon spray, tire shine chit, Armor All, 303 Aerospace, etc, etc.
In the past, I have always had best results with 303 Aerospace. I did, however, recently try "In & Out Spray" from Adam's Polishes. Adam's recently brought back this product after a few years of its being discontinued.
I am glad they brought it back! This stuff is truly great for what it is designed to do! It dries ... doesn't stay "greasy" and don't have to worry about getting over-spray on paint or windows! ... it just wipes off and doesn't leave any kind of smeary-residue crap! I love it for getting way down into A/C vents and other tight/inaccessible places!
Check it out:
Adam's In & Out Spray Dressing