cheap method: scuff it up with a 3M scratch pad, wipe with naptha, spray paint
If the ball doesn't touch the apron at all, this is the way to go.
Not so cheap method: Take it to a powder coat shop. They can sandblast and coat black. Black is a very common color for shops, so it's usually quick and fairly cheap; it's the labor to sandblast that gets ya.
My opinion: The gold apron color that you have isn't half bad. That gold powdercoat lockbar and rails though... Gold is a tricky 2-part powder process that very few shops can do (even the "experts" that advertise on pinside). Unfortunately, brass plating is probably the best for a gold look.