we used a load of cardboard boxes that we basically 'battered' with our fists into hilly shapes, then covered with newspaper and painted - sponge on for a more 'grassy effect' - or use a blend of green powderpaints sprinkled on.
use the rough green bit of kicthen sponges for bushes, trees etc
seasponges for bushes too
buy a bag of fish tank gravel and glue and use to make country wall and rocky areas.
and foam board for the buildings and stations etc.
expanding foam is also good for odd shapes, and you can carve it up too.
you can also put thing in the blender to create textured surface material - to be sprigs, twigs etc on the hills.
depending on your scale you can you rock salt for the gravel under the train - add a bit of dry soil to mixture and stir so its not too white.