I would use a premium chrome polish, the kind in a tube. I have had good luck with it and if you wipe carefully, it won't leave any grit behind. It seems to cut the blackened oil quite well. My polish smells like petroleum base. I got it from a friend and don't know where you can find it.. The name is "Congress" Made in Germany and imported by Congress Tools Co., Inc.- Naugatuck, Ct 06770-1009. Says it contains aluminum oleate, whatever that is. It is excellent for shining up dull face plates, needle plates and bobbins. I have had no bad results at this time. Used it on a dull Kenmore plate and it now looks like a mirror.