Electrical Contact Cleaning

What I did with my headlight connector when I replaced the plastic part, was soak the terminal ends in vinegar, then baking soda water.

I tightened up each terminal then inserted them in the replacement plastic.

I don't see any reason you couldn't soak the entire connector, plastic and all, in vinegar, use some bottle brushes in the terminals. Then rinse in baking soda water. If you can tighten up the terminals all the better.

I would blow out the connector with compressed air when done.