[PJL]

If it's a wafer switch type I do quite often strip the whole switch down and refurbish the wafers.

Once the wafer is out, Viakal (domestic limescale remover) is a brilliant cleaner and will strip the oxides off in seconds. As it is strongly acidic so you need to rinse plenty of times afterwards and finish off with Servisol or a very light oil.

Viakal is a gift to radio restorers (providing you can rinse the item heavily afterwards) and will strip grease and remove oxides on metalwork in seconds. Unless you have tried it you would not beleive how quickly it cleans brass. I tend not use it on painted surfaces for fear the acid would run underneath and erode the metal over time.