It will take many hours. Use wet n dry. It will help keep the dust down. Sand in a opposite direction for each grade. Sand until all scratches from each grade are gone. Then move to the next finer grade. Repeat this process using finer and finer grades until you get the finish you want. If you are not after a chrome finish, then you could get away with half of the above grades. You need to seal it with either a clear lacquer or get them anodized, otherwise they will oxidize.
Nitromors
80 Grit
120 Grit
220 Grit
240 Grit
320 Grit
400 Grit
600 Grit
1000 Grit
1500 Grit
2000 Grit
Buff
Clear Lacquer
It will take many hours. Use wet n dry. It will help keep the dust down. Sand in a opposite direction for each grade. Sand until all scratches from each grade are gone. Then move to the next finer grade. Repeat this process using finer and finer grades until you get the finish you want. If you are not after a chrome finish, then you could get away with half of the above grades. You need to seal it with either a clear lacquer or get them anodized, otherwise they will oxidize.