I wouln't have used the old WD-40 for that task, it's not a good cleaner and will actually attract crud. I would have used a good electrical contact cleaner to clean them up and then lubed it all up with a few dabs of Di-electric grease.
Electrical Contact was not an issue. I used WD40 Water Resistant Silicone Spray Lubricant mostly to flush out the years of dust and crud. I repeated the spray and air jet several times until it ran clear.