[KCV6]

The best coating for durability is E-Coating such as clearclad. It is what all the big manufacturers use for window frames, switchplates, door handles etc. It is a high water content conductive paint emulsion that is deposited on the item much like electroplating. the part is dipped in the liquid and a current passed through the liquid to the item. This causes the coating to deposit in a thin layer until the item no longer conducts. This gives a perfectly uniform finish everywhere on the item. The item is then removed from the bath and baked much like powder coat. The problem is it's hard to get. It Comes in clear and all sorts of colours and is often mistaken for an anodized finish.

Next best bet in my opinion is 2-Pack Urethane paint, it is however toxic and should be sprayed in a proper spray booth.

Standard clear acrylic aerosol paint is an option, but it isn't overly durable compared to the other two options

Regular waxing/polishing works and the beauty of nickel is it can be polished with a mild polish like brasso or silvo many times.

Cheers

Mark