I would not use any spray until you get as much as possible out with air. Wet sand sticks unless it is very wet. Add in an oily mixture like wd-40 and it will stick forever. If you are talking about the pigtail I would disconnect the battery in the trailer, unplug the camper and dip that pigtail into a bucket of water. Move it around, shake it, force water into it maybe even use a hose to flush the sand out. After it is clean hit it with the air to get it dry. Then add whatever you use on your pins normally. But if you are going back to the sandbox I wouldn't put any lubricant in there unless you plan on putting a plastic bag over it when not hooked up. And it wouldn't hurt to wrap it with plastic when it is hooked up.
