i have cleaned them with a microfiber soft polishing rag
a q-tip used lightly, cause it will scratch
99.1% rubbing Alcohol, when i got my fingers on them
Air compressor , when it was just dust
soap and water , when it was metal
Waxed when it was metal.
some of these cheap plastic reflectors die fast when you have to start messing with them in any way. they can just fall apart literally, the best for them is to be very nice. some of them suck so bad, the thin layer isnt even complete.
metal reflectors are like , , , well like metal they are very durable but can still be scratched.
Chrome could potentially be re-coated on a chromed metal reflector, plastic can be replaced. there are Chrome paints, but nowhere Near the reflective quality needed.