This will make a petal that looks waxier than a single thickness, and it feels a little like styrofoam when you're shaping it, so it isn't quite as fragile as a single piece.
First, get two pieces of wafer paper that have the same shape. (Cut them out together to make sure they're the same.)
Put a wire on the petal.
Place the second petal on top of the first, being careful to line it up exactly on the edge. Once it's put in place it's going to be hard to move it, so try to be as accurate as you can the first time.
Now you have a wire between two petals. The paper should be getting soft at this point.
To give the petal a cupped shape, pinch the base of the petal.
As long as you didn't get the petal too damp, you should be able to press it into shape at this point. You can twist the edges to give them some movement.
You can also put the petals on a former to allow it to dry with a certain shape. Let them dry completely.
Experiment with the different types of glues to see which one you prefer. The piping gel and gum glue dry stiffer than water, but don't make the paper shrivel up as much.