I would advise against using latex. When you're making wings, there are two critical issues you have to deal with: gravity and wind. You are always going to have gravity pulling down on the wings, and latex will eventually tear. Worse, latex that is thick enough for what you want is heavy, and the heavier the wing is, the heavier your struts and mountings are going to need to be. You also have to deal with wind, which can be as little as the breeze from an A/C vent. Wind pushes laterally against the wings, and coupled with gravity places even more stress on the wing material.
The best wing material I've found is a brown nylon shower curtain. They are lightweight, about impossible to tear, paintable, waterproof, and cheap.
We made the wings for our Jeepers Creepers Creeper out of two curtains and some PVC pipe. We used red and blue Sharpie markers to draw on veins and arteries and used flat dark brown and black spray paint to add highlights:
They held up great, but as light as the PVC was, it made the wings too heavy. These are the Gen II wings we made, using 1/2" bamboo struts in place of the PVC. Made them much lighter and easier to handle. And as you can see in the two pictures, the reduced weight allowed us to angle the wings higher and look more imposing.