Option 1 -- Take the ball to your local pro shop and pay the $5 or so to have it done professionally.
Option 2 -- Spend a couple hundred bucks and buy a spinner.
Option 3 (by far the poorest option) -- Using a circular motion, sand the entire surface of the ball using the desired color Scotchbrite. Rotate frequently to avoid flat spots. When your arm wears out, stop for an hour or so, then resume. Repeat until you have a uniform job.
JohnP