I have used Duraglit metal polish (cotton wool type) on plastic in the past, then a light t-cut. be gentle and it could work for you, try it on a small area!
duraglit works great on plastic but when i tried it on my visor its like it has a protective layer what it removed what is now visible
yeah its the uv protective layer stops the plastic oxidising and going yellow and brittle, same as plastic car head lights and such