Cheers,
nice project, although a little on the small side. I've been thinking about airships for some time now, and the skin is always the difficult bit. The paper RC-guys use is very light japan-paper, which can probably purchased at an arts-and-crafts store. It is glued to the framework using wallpaper-glue, and then made damp using a plant-sprayer. Then it will tighten itself around the structure. Once dried, it can be made a bit more durable by painting it with clear dope (not the kind you smoke). I haven't tried the method on a complicated, 3-D structure like an airship, but it worked fine on a glider-airplane, and it looks fantastic, it's half-transparent and shows off the inner skeleton when seen against the light, conveying a lot of the early-days-of-aviation feel.