I've used Armor All for cleaning gauge faces - helps protect the paint from futher deterioration. I used clear AA Detailer's Advantage (which was also a recommendation from my convertible top installer to use on the top fabric) - I use it on ABS items as well (fan shrouds, even rubber hoses). Good stuff; if you're hesitant to use it, try it on an old part first - I think you'll be impressed.
Mother's Plastic Polish is great for plastic or acrylic gauge covers - not abrasive, but designed for see through plastics (like convertible rear windows). Anything with an abrasive in it (like toothpaste, which sometimes contains pumice), will leave a haze or swirl if you're not careful.
Just my opinions -