Good luck to you. But what is the point?
I totally admit this is completely a sort of passion project... at least on the surface of it. I think I initially polished my kettle just to see if I could. Then, it turned out that I actually wanted to brew more, as silly as it sounds, partly just to use the shiny keg. Here's the strange part: I think I actually took brewing more seriously and brewed better beer because looking at the keg reminded me that if I took the time to do something as seemingly pointless as polishing a keg, then how much more attention I should pay to the other elements of brewing that 'really matter'.
I've heard some people say that the beer they brew is a reflection of themselves; this takes on an added layer of meaning when you literally see yourself in the kettle you're brewing with! Lol! Anyways, it's true, it does take a couple hours to polish a whole keg depending on how clean the outside is to begin with and how much a of perfectionist you are, and you might fully benefit more from doing something else with those couple hours. But then again you have a polished keg for the rest of your life--- and then there's that reflection of you starring back reminding you that if you took the time to do something as seemingly pointless as polishing a keg, how much more thoughtful you could be with the rest of your craft.