I don't have any personal experience with any of the sprayed in bed linings but my grandson owned a Red Dodge Ram 4x4 a couple years ago. He had done exactly what you described, sprayed-on lining on the lower one foot or so below the door trim strips. Being a youngster with a high salary he trades trucks every year or so and didn't keep that one long either but when I saw it the truck and spray-on lining looked good.