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An old toothbrush and some diluted simple green, or bug and tar remover.
Than a light coat of some plastic cleaner. 303 is the way to go but Turtle Wax F1 or Armor All if you really want to).
Another thing that works well at cleaning the bugs off of the textured plastic mirrors is #39 heavy duty vinyl cleaner. I use that and a microfiber towel and they come right off. It may be a little hard to find #39 at your local retailers though.