A thorough cleaning with alcohol or Prep-Sol (painting solvent) should clean the trim sufficiently to accept a surface coat. The chrome could be scuffed using fine steel wool as well.
We always used SEM Bumper Coater which gives a durable satin finish and matches the finish of Volvo's bumpers or the black mirror housings.
It seems to last about 3 years on bumpers and trim pieces. Longer if the sun exposure is limited. Some chrome parts we painted in 1994 on the convertible 242 my friend has are still a nice black except where it's been physically scratched.
I don't know how other brands work. The SEM product has all kinds of good chemicals in it, like Xylene. Dries in about 30 seconds too.
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total