From what I can tell VN's Flex-Skin is the same as Thin-Skin which most fly shops carry. Basically a very thin Sili-Skin that is not adhesive and comes in a variety of mottled and plain colors. The Nymph-Skin looks like pre-cut Flex Skin. Most people use this stuff for nymph wing-cases or scud backs...not sure what your intentions are here.
I bought some of the stuff when it came out but am unimpressed by the way it looks for a wingcase - too shiny and synthetic. I prefer the good ol' Turkey Tail sprayed with fixative for wingcases...or a bit of marabou.
I haven't seen the adhesive backed lead. What would you use it for?