This is my double tissue hummingbird, modeled from Robert J. Lang's Origami Design Secrets. (See his version of the hummingbird here.) To enhance the curvature of the wings and the overall elegance of the model, I wet folded the paper. Wet-folding is most effective on animals and other organic objects because it offsets the stiff and geometric quality of traditional origami folds. To wet fold, I use Elmer's Craft Bond Paper Craft Glue Gel diluted with water. I haven't figured out the exact glue to water ratio, but further experimentation will get me closer to the desired mixture. For now, I just have to make sure that I don't apply too much liquid on my paper, or else I run the risk of tearing it.
My biggest challenge with the hummingbird was shaping the body--especially the tail. The nice flared tail you see now took many tries. For the longest time, the tail lacked any curvature and just looked like an unsightly rigid protrusion. The next time I attempt the hummingbird, I want to use black and orange (or perhaps black and pink) double tissue paper/foil.