I've recently taken up with yet another approach: making tarps from plain white copier paper cut to over-size and soaked with dilute PVC glue. Drape to fit while still moist, let dry, and paint!
The advantages of copier paper are that it is thin (standard thickness around 3.5 thou - like most PE) and the fibre-grain is very fine, leading to nice scale thickness (1/35 canvas should be, what, maybe 1/300 or so of an inch = about 1/10 scaled inch, or less, thick? 1/300 = 3.3 thou or 0.0033 inch... right about copier-paper thick!), cheap, easy to work with, and will have less of the fuzzy-edge and visible fibre problems than seen in tissue tarps. The PVC and later painting of course further seal the surface and gain scale texture. Also, because you fit it while wet, it will easily take up close form to stuff it drapes over... Paper tarps can easily be "reinforced" (as in simulating added thicknesses and repair-patches sewn onto the fabric) by simply adding a real layer and then stippling around the edges with a pin to show stitching. Likewise, it is easy to create the sewn joins of panels, etc., by realistically cutting the piece along the desired join and the over-lapping them for the seam while still wet - do some pin-stippling and you are good for a seam! Paper tarps take any paint quite readily.
I have no ready route to post a sample pic of this, but recently used it to great effect on my Tamiya Horch 1A flak-truck, where I scratched a rolled tauna-cover (rag-top) on the folded frame, and on my flakpanzer IV wirbelwind, where I created one of the "bed-sheet camo jobs" done in the winter of 1944 / 45. The paper "sheets" - properly once-white but now grimy and torn - were draped over tools, across the turret, over areas of the hull, etc., and, after drying, revealed the edges of the covered items - just like a real sheet would!
Try it out - you may find it what you want in the scale tarp quest!
Bob
Bob