I didn't apply anything to it at first, then decided to apply the Refinish/Restore stuff. It's held up well (contrary to how it's held up on the rest of my cladding...but that's in another thread...)
I'd try the Aerospace Protectant 303 since it seems like it would absorb to some degree and it gives a nice rich matte finish with no greasy residue at all, and has SPF40 to protect it from the sun. The insert isn't plastic, but I can't recall right now what I've read it's made of...fiberglass maybe??? anybody recall right quick?? And I can't recall if it's painted or if it's solid gray throughout.
I was waxing the hood the other day with the ICE polish by Turtle Wax and accidently hit the insert a bit....it showed up on the insert just like you'd expect an oily rag would leave a mark....I buffed it with a dry rag and it blended right in and looked good. Which makes me think the R/R is NOT an impermeable coating...