Although I've never used it, Eastwood makes a plastic restorer that is supposed to work pretty good. Been meaning to buy some for the Durango trim. It's on sale right now too. Another option is to clean the hell out of it with ammonia/water and Krylon Fusion it. Have had great luck with that stuff.
Hopefully there's not paint damage like mentioned. Off the shelf, Meguiar's Ultimate Compound with a mildly aggressive foam pad will cut most junk off by hand. Zaino PC Fusion works great too but has to be ordered. If it's on the glass, I've had good luck with ceramic cooktop (stove) cream cleaner when nothing else worked.
This hood has a poor repaint and clearcoat job, and was neglected for several years other than some drives through an automatic carwash. Pics are before/after using Ultimate Compound and a foam pad. Below that is an '86 F150 that I bought and fixed up for my dad for Christmas last year. That's original single stage paint that was pretty rough and chalky when I got it and had some "unknown substances" on it, also done with Ultimate by hand.