Hi,
For things like silk or snakeskins, I like a thin but consistent layer of glue, so I use one of those foam brushes. I paint on a nice even and smooth layer. Start from the grip, clamp the end, and work your way to the tip with your finger to flatten the backing, removing all air bubbles and excess glue. I don't usually put a layer of glue on top of the silk after, just whatever finish I'm going to use.