I have always found cork roadbed or Woodland Scenics foam roadbed to be very easy to work with. It easily follows whatever path you choose and can held in place by nails, screws, glue, spray adhesive, or whatever your favorite method might be. I also agree that reusing it is not impossible, but only if it is not too old and become hard and brittle. I wouldn't plan or reusing it, but if you are consider it a bonus.
Art