Ferule looks pretty normal to me?
Only the lightest of etches, probably a wipe with vinegar or half a fruit (wash, dry well, and oil afterwards), would remove that light rust; the surface is basically clean and clearly etched already. To bring up the pamor significantly better would involve staining, so some layers are black and others silvery. This is a process involving arsenic
Some forum members have some knowledge of the matter though, and can maybe advise you further.