Hi mate.
Aerospace 303 gives a nice natural finish. And chemical guys silk and shine does too
I find that if you srcub the plastic area in question with a fairly strong solution of apc and then dry before applying your chosen product will give you a far better finish.
Same applies to the tyres, i spray them with AG engine cleaner, scrub then rinse. You'll be amazed what comes off them, leavin you a nice base to apply your tyre dressing.