Slow, I can't say for sure because I have not used it on nickel plate, but for other metals I have had good luck with a product called
Never Dull (clicky). The web site says it works on nickel.
It is a very soft fiber impregnated with lubricant and polishing materials. It is way finer than the finest steel wool.
I would use a little dish soap and water to remove any grease and grime first, then try the Never Dull on an small out of the way spot. Rub it on a bit. It will make a fine black slurry, gets on your hands, then wipe with a clean dry soft cloth rag, like an old T-shirt, until the residue is gone. She will shine with a little elbow grease.
A small piece goes a long way. I have had the same can on hand for many, many years.
Have fun and don't forget the pic's.