"shop I used to work in had this dip for tool handles... you took a tool with an uncomfortable metal handle and dip it."
Again, most likely the liquid electrical tape which is used to insulate screwdrivers and the like in order to help prevent electric shock. It makes a great all purpose coating... I never thought about the bedliner stuff but it makes sense. You can pick up a can of the liquid electrical tape at most hardware stores and even Mall*Wart I think, in various colors for about $5.
When you say "uncomfortable metal handle," I imagine a hammer wrapped in barbed-wire. :p
As for my motivation to use it, it works great to coat metal pieces like a bike hanger so that the metal doesn't scratch up the frame. I imagine it would work pretty well as a weather proofer and the spray on bedliner definitely is.