I'd use something like Autosol or Mother's Mag & Aluminum Polish. The Autosol is bit thicker and easier to work with being a toothpaste-style tube, of which I just use the regular version, but there is one for aluminum as well.

Mothers -
https://www.repco.com.au/car-care-p...-aluminium-polish-140g-655100/p/A9432579

Regular -
https://www.repco.com.au/car-care-p...sol-metal-polish-75ml-art1000/p/A4345053


Specific for aluminum -
https://www.repco.com.au/car-care-p...ol-aluminium-polish-75ml-1824/p/A9707087

You can use this with your Dremel, but a toothbrush and cue-tips come in handy as well. I'd probably go over it with a wire brush first to level the surfaces down, then progress to polishing.

I use this method on mufflers as well, in this case with the Mothers and a polishing cone attachment.

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