Brushed aluminium

Use a hand belt sander(3/18,3/21 ,3/24, 4/24) with soap/water,(belt base must be material and not paper) grade 100 =fine 80= regular 60=special(not easy as others) All info above are for soft aluminum.,myself I am using a 4/24.(4inx24in),and use clear mat
spray can for protective coating.