I put the truck on a lift at the service station and sprayed Salt-X thoroughly - before leaving for Speedweek. We ran in rain each of the three days getting to Bonneville, so I assume a bunch, if not all, of the Salt-X got washed off. It's water soluble -- so the rain could do it.
So when we got home I looked and there wasn't much salt. I didn't spray under the truck. We got done with the long traveling in mid-October and drove the truck around Marquette County during the next month, hitting rain, slush, mud puddles, and so on. Last week I crawled under the truck to do an oil change -- and sure enough the FRONT of exposed surfaces were pretty clean of salt. But the back, and up on the top of things like the transfer case, were still coated.
Ergo: Driving in the rain and sloop is not enough to get all of the salt. I'll be taking the truck back to that lift next week to do a proper cleaning of it.