Its interesting that you brought up lens shapes, as one of the more interesting shapes that happened was one droplet that had dried as a concave surface. I thought it was pretty cool, but it wasn't usable as when I was playing with it, the dried glue droplet popped off the aluminum tape.

Creating the bubble style lenses is pretty difficult, I have been trying with a small straw, using mouth blown, and compressed air, but its a bit too delicate. The only way that has worked is to coat the tip of the epoxy tube, and squeeze a bit of air out of the tube and epoxy at the same time and hope you form a bubble. The process is similar to the bubble wand style toys kids play with, you have to coat the wand surface with a layer of soapy water in order to create a bubble with it.

I have been trying to induce different surface shapes by manually pressing on the material as it dries, and also using compressed air to change the surface while it cures into a more viscus fluid, which does seem to kinda work.