Sheperd Paine in itīs Modeling Tanks and... from Kalmbach Books describes a very usefull tip for making sandbags passed to him by a guy named George Rees. He says that you can use Chiclets (yes chewing gum !). The big ones for 1/35 and the small ones for 1/76.
Soak the pieces of gum in water to disolve the hard outer shell, leaving the soft core wich can be textured the same way than the epoxy putty sand bags. Then draped in the disiered position. Once dry (the gum hardens rapidly) you can paint them.
I will give this a try