You should chemically treat it to remove the shine. Naval Jelly is caustic enough to do it but any oil or silicon must be totally removed first in order to get an even finish. Don't use an abrasive pad or sandpaper.
If you try Naval Jelly don't leave it on too long. You can reapply it a bit longer the second time to get the desired finish.
You can also submerge it in full strength vinegar to attain a muted 'french gray' appearance. Duration of the bath is also something you need to keep an eye on.
