The original MrClean sponges work great, for the really aggressive, age baked stains, I suggest a combination of Simple Green/water at a 30/70 solution with a cloth baby diaper. Diaper should be lightly damp, not soaked. Be patient, work each item, do not clean in the direct sunlight, cool shaded area above 60 degrees will be your friend. When you come to the door panels, be extra gentle, do not put a lot of weight behind your cleaning, or you may crack your arm rests, if they are not already cracked.
Bill S.