After cleaning 30 years’ worth of crud off of all of those little electrical connections, they need something to keep them from corroding again. Contact grease is specifically formulated to prevent corrosion and to improve electrical connections. Do not confuse this stuff with dielectric grease, which is designed to stop voltage from escaping, such as around spark plug boots. In a pinch, anti-seize compound will do, since the metal will improve connectivity and the grease will fight moisture, but it tends to be a bit runny, while contact grease will stay put. I get it from Eastwood’s and one little jar will last for years.