I had not thought about this in years, but this thread has sparked a memory. The A-Yard at San Bernardino was on a westward ascending grade, increasing as tracks moved westward. During the citrus loading season, "turns" would go west on the Second, Third, Fourth, and Redlands Districts with pre-cooled, iced reefers and return with loaded ones, yarding them in the A-Yard. The top end A-Yard switcher would have to drag out heavy cuts of perishables, and the little Alco S2 switchers did not have the greatest sanders. So, when I worked those jobs during the produce season, I always scooped up a pile of sand into an empty coffee can, and stepped out onto the back platform to sprinkle extra sand down when the engine was on the hardest part of the pull. It actually made a difference.
As information, there are usually piles of sand wherever locomotives tie up, from Engineers testing and cleaning out sanders, etc. Normally, they are a nuisance, but -- sometimes -- handy. 
