I have this same project to accomplish. 1968Z28 clutch dated 11/2/1967
I use this series of chemicals in conjunction with basic soap & water. As far as scrubbing action I use a 3M scotch-brite greenie pad &/or Nylon and at the most a brass bristle brush.
THE KEY is the Alum Brightener chemical. PPG DX501.
as usual using the correct PPE, Personal Protective Equipment. - Safety First.
Jim