In the Halfland sky there are a couple of monofiliant lines to run dimensional clouds in front of the painted versions. They can be moved along like clothes on an old fashioned clothesline via pulley. The clouds can be lit from the front or sides or behind with white or colored lights for changing time of day or type of weather. NICE!
They are made with loosely arranged polyester fiberfill encased in a skin of white tulle (sheer netting fabric) and stitched closed. They can run along the line being pushed by hand with a drinking straw embedded inside and threaded on. (An idea suggested by a workman hired to help on the set for a day several months back) Or they can be glued firmly onto a double pulley line and pulled across the sky.
On the right, a cloud is photographed behind the plastic sky scrim. I like the realistic shading this technique gives the cloud shapes and how dreamy the sheeting makes things seem.