I have found that the very stubborn ones can have oxidation removed quickly with 220g on a DA sander, then OOOO steel wool, then buff on a bench grinder with buffing rouge. Any rouge that is stuck on after buffing easily is removed with mother's aluminum mag polish. Maybe not a solution for everyone, but they come back to mirror in about 15-20 minutes per leg.
Left is complete after buff, middle is intermediate da sand, right is how they looked before any work done to them.
Sent from my iPhone using
Weber Kettle Club