Ok - clarification required
1. The barrels are new/NOT anodized/polished aluminum, right?
2. You say that they're sealed...not sure if you mean anodized and sealed, or sealed with tape etc.?
3. If they've not been anodized, then simply polish, degrease, anodize, color and seal.
4. If they have been anodized, strip the anodize layer with the stripper, polish, degrease, anodize, color and seal.