Having read your recent articles on scenery,  I would suggest use use ordinary screen wire to form hills and valleys. I use coat-hanger wire to create the top contour; fasten the screen wire to it with U-shaped bits of wire, and then lay 4" squares of 2-ply paper towels on the screen after dipping in soupy Hydrocal B-11. (This dries to a harder surface than plaster, but takes acrylic colors just as well).  Rock molds filled with thicker Hydrocal are applied to the towels-on-screen-wire, after spraying dried towels to assure adhesion.

     The screen wire is very easy to form into contours for hills, etc/, and allows more, and subtler variation than cardboard strips and tape. I use this method on my home layout, and on the Glendale Model Railroad Club, where I have been a member for 65 years, and done the scenery for some 40 years.