For stripping the anodizing off of aluminum it is best to take it to a professional anodizer to have the coating removed. the chemicals involved are harmful.

Sand out scratches with wet paper. 120 grit will probably take out most scratches. You'd have to go coarser, if the scratches are deeper. Finish sanding it to 320 grit.

Buff with a ventilated flap wheel with Tripoli compound. Clean that off with some thinner. Buff again with a ventilated flap wheel with white rouge. You'll have a good shine going then.

Finish with a Canton soft buffing wheel and white rouge for the brightest shine.

I get the ventilated flap wheels from a local tool shop.