Tarp Freight is easily made using soft thin paper like facial tissues. Use one piece and place it over the material to be covered. This material could be actual parts or just shapes of wood, plastic, rubber or anything that will look like freight when covered. You can use skids or nothing at all to put the freight on. Whatever you use place wax paper underneath it so when the glue is dry it will be able to be removed easily.
Brush on a 50-50 mixture of white glue and water starting at the highest part and brush down. Try to do the 4 corners first. Try to work quickly and be carefull not to break through the tissue ... the less brushing the better.
When dry cut off the excess and paint them a flat gray, blue, green etc.
These make good looking tarp covered freight that can be used all over the layout and even on flat cars.