Not sure if this is exactly what you are looking for, but your post reminded me of a video I saw recently. A detailer wanted to remove some scratches and dullness from his B-pillars. He used a DA polisher with a polishing pad and a polishing glaze from Xtreme Solutions called LVR 403. LVR 403 is an acrylic glaze that can remove some fine scratches and also fill scratches with an acrylic resin. This might work on your trim piece. Just make sure to not wash the area with any soaps or cleaners for at least 48 hours after application to give the acrylic time to cure.
BTW, I have used LVR 403 on my wife's Honda's paint and the results are awesome. However, I have not personally used it on trim.
Here is the video: