Wax paper texture is a neat way to add texture to rocks, mountains, foliage, etc.  To create texture like that on the mountain in this painting, I first traced the mountain shape onto the wax paper.  Then I cut out the shapes and tore them into smaller pieces.  I added a thick layer of paint in different colors to one small section and then placed a piece of wax paper over the paint.  Finally I added a drop of water under the piece of wax paper to make sure that the paint was wet enough for the wax paper to stick to the paint.  I continued on in the same fashion for the remainder of the mountain.  Then I let the paint dry all the way.  Afterwards, I removed the wax paper to reveal the design.  You can also crumple up a piece of wax paper and place it over wet paint, weigh it down with a book and once dry, remove the wax paper to see the texture.