Top answer your question directly, find a sanblasting shop and have them do it. It would take virtually forever to remove all of the powder coating from all of the nooks and crannies by hand.
But before you do that, which will likely be expensive, consider a silver painted finish. If you take them to bare metal you are going to need something on them, a clear coat at least. I would just scuff the powder coat lightly with a scotchbrite pad, clean well with mineral spirits, and spray paint silver to get the look you want. Then you do not need to remove the original powder coating.
Or take them to an auto body shop and ask what they would charge to spray them with some left over silver paint. You could even ask about epoxy hardeners and/or other additives they could add to the paint to make it hold up better on wheels.
