If you're worried about water intrusion into moving parts (which can lead to icing), then WD40 is the answer. Spray some into your door locks, for example, then work the key in and out a few times to ensure all parts are coated.
Otherwise, the best low-temperature lubrication is graphite. Teflon spray is also good for low-temp lubrication, but make sure you get a dry-film Teflon spray that doesn't contain silicone. It will look like a white powder when sprayed.
Non-moving parts need no lubrication at all, so limit your lubrication activities to hinges, your jack crank handles, etc. that have moving parts.
For the electrical connections on the trailer tongue, dielectric grease works to keep water out. It's non-conductive, but when you plug in your umbilical again, the friction on the contacts will scrape off the grease from the contact points so it won't interfere with your electrical connections.
Engineering: Finding complex solutions to simple problems you didn't even know you had.