my exhaust doesnt have any marks on it as such, was just dirty really and i've it done 3 times since i put it on the car and its as good today as the day i put it on the car to be honest.
use autosol or peek metal polish either product does the job
brillo pads are perfect i always use them....
my new exhaust all cleaned up
used autosol myself last week, brilliant stuff. alro cleans up fromt mounts and any metal under the bonnet