Don't be too heavy on the wire brushing. If you put scratches in the surface it provides a perfect key for the marine wildlife. Fine grade emery cloth and elbow grease is the best answer.
I've been using a rotating brush for years now. Not a wire brush, but one with synthetic fibres coated with carbide powder or similar . Has "Triplex - Polybrosse" stamped on it, and is about 8 cm diameter. A fair bit finer than a wire brush that often leaves scouring marks, but faster nevertheless. The orange version leaves a satin matt finish, blue version buffs to shiny satin.