Just get the buffer wheel for a Dremel and some Mothers Aluminum polish https://www.amazon.com/Mothers-05101-Mag-Aluminum-Polish/dp/B00068GEJM?th=1
If you want to go balls out sand it with 400, then 600, then 800, then 1000, then 1500, then 2000, then 2500, then 3000, then some 0000 steel wool...