Hi,
Last weekend I was helping out at the NMRA (BR) Railroad convention and managed to take a short video of some amazing terrain on one of the layouts. The layout was called "Beer and Grain" and the owner was also giving a modelling demo of their scenery techniques.
http://www.youtube.com/v/E4SYwRgVZmU?fs=1&hl=en_GBThe hills are polystyrene blocks, carved and formed with a knife and "shorformer" with filler applied as a texture coat. Once dried, an emulsion (latex) paint was used to colour the features and selected dried gravels liberally applied areas of white watered down glue. The bushes are "woodland scenics" and the cacti are whitemetal castings.
I enjoyed the event and I am only sorry I didn't get a chance to video an "in progress" piece.
Ramirez