The active ingredient to remove anodizing is sodium hydroxide. But be very careful, it is very caustic and can burn your skin and eyes. Use protective gloves and eyewear. I anodize and strip anodizing for my fly fishing reel business. Always test first, the sodium hydroxide can actually etch away the aluminum - and I DO mean etch it completely away so that it no longer exists. Especially be careful if the channel area has not been anodized. If not, you need to protect it some way. A thin coat of paint will do the trick and can be removed easily afterwards.
For a protectant after polishing, I always use
Renaissance Wax on my aluminum reel parts. It will keep the shine for years even with daily handling and weather exposure.