Try Apoxie putty. Wonderful stuff when you learn the tricks. Mix 50/50 part A & B.
Squish it between thumb and forefinger until you get a neutral grey color. Roll into a nice little ball and let it set for 10-15 minutes (or it will be too sticky to comfortably work with).

To make a vehicle tarp or bedroll, roll the ball on a flat surface until you have a "worm" the length you want to fit your model. Now a neat trick..cut the "worm" into equal pieces (4 or 5) and roll each piece into a ball.

Now stick the balls together and mount on your vehicle, pressing lightly against the surface. There is enough stick to the epoxy to do this. The separations between the balls will simulate the tiedown creases in the fabric of your tarp. You can place thread in them now. With a toothpick or some other tool (I prefer toothpicks because they are always handy...)you can now press into the epoxy more creases emanating out from each segment line. On the ends use the tool to simulate a rolled fabric. This is very easy to do and you will have enough putty from one set to do many, many models in 1/72nd scale. Here are examples of tarps and backpacks I made with Apoxie when I first got this material. It was a pleasure to work with.




Hope this helps you.
Cheers

Ed Okun