If Dirk had good results re-chroming his mirror, I’d follow his lead. He’s done an amazing job with his car. Also the method of stripping,then plating in copper, nickel before chrome really produces the best results as Colin said. Sadly, California has so many environmental laws that it’s difficult to get anything plated here.
As to the chrome air vents: I would not disassemble them. Others have tried and have said it’s difficult and parts are easily broken. I have found that an ammonia & water solution does a good job of initially cleaning the chrome parts. Use soft cloths, foam paint brushes or detailing brushes to get in tight corners. For me, Flitz brand metal polish is the least aggressive and produces the best results. After polishing I spray with a 50:50 solution of IPA:water and wipe off with a clean microfiber cloth. Just go easy and take your time.