As to the question of fabric type, I would suggest that you consider a Tyvek soft structure "fabric" (Google Tyvek 1443R). It is very lightweight (at 1.25 oz/ sq yd, it's lighter than silk and much lighter than cotton). One of the great things about it is that you can work with it like any other fabric, but it doesn't unravel. You can DIY whatever you want, if you're so inclined. It's also water resistant but still breathable, making it excellent as a groundcloth, wrap, or emergency tarp.
I simply cut a flat sheet large enough for any bed that I would encounter on the camino, sprayed it with permethin on the underside and about 8" on the topside edges, and sewed reinforcements for addition of grommets so I could pitch an emergency tarp with my walking poles if I had to go to ground for some unexpected reasons. Even with a couple titanium stakes and guy lines, it's still less weight than a simple sheet and far more useful.