Use newspaper or those brown "industrial" paper towels. The kitchen ones are much too flimsy, and cause issues when dippiing them in the plaster. Cut the newpaper into strips about 1.5-2" wide and 6" long. Mix your plaster to the consistency somewhere between pancake batter and white gravy. Dip the strips of paper in one at a time until they are completely sumbmerged in the plaster. You don't want any dry paper. As you remove the paper strip from the plaster, run it between your fingers to get most of the excess plaster off. You want it so be slightly drippy, but not have plaster running everywhere. Next, lay the strip on your layout, and smooth in place with your fingers. If you mix the plaster to thin, the final product will be weak, and if you mix your plaster too thick, it will be difficult to dunk the paper strips in. Once the entire area is covered, mix a thin batch of plaster and pour it over the scenery. let this harden slightly, then as it most of the way set up, use a cheap 99 cent 1-2" wide paintbrush dunked in water to smooth the surface. If the plaster has not set enough, the plaster will move too easily and gob up the brush. If that happens, let the plaster harden another few minutes. You want it hard enough that it takes considerable working with your wet paintbrush to smooth out your landscape.
kevin