kinsaka;
As posted above, ordinary toilet roll will disintegrate when wet (by design) What I have had really great results with is tissue paper that comes with a new dress shirt or from a gift shop for wrapping china. It is very sturdy and comes in a large enough piece to make nearly any "fabric" object.
As above dilute white glue in a 50/50 mix with water first. Dunk your object in the mix. Form the object and let it dry in place on the model. Do not try and form a dry object to a model, the results are very poor. If you're doing a tarp over items remember to give the tarp some "gravity" press it down to contact the tops of the items it is covering. As well an insecure tarp will blow off a moving vehicle. "Secure" your tarp with a fine string. I use the cords from tea bags. I brew up a pot drop the bags in. When the steep is done I pull the bags out. Pour some of the fresh tea in a shallow dish and "dye" cords from the teabags. Makes realistic looking rope and is very close to scale for 1/35. I then place the bags flat to drain and dry. Tea leaves work great for diorama bushes and trees.
Now once I have placed,secured,gravitied my tarp. There is one more step I use to mask the telltale nature of tissue paper when painted. I take my trusty bottle of "SPRUE GOO" (diced sprue in liquid cement that liquifies over time to a thick paste) I take it down from the shelf and layer it on the tarp to cover the texture of the tissue and give me a smooth surface to work with in the paint phase.
When done it hardens and allows the items to appear to be all one piece (some almost looked like resin castings) Then it is just a matter of painting and shadowing etc, etc,.
I hope this helps. Any questions please feel free to email.
Cheers;
Gregory