LOTS of paint. LOTS.
Midna is such a cool character and I could not resist cosplaying her. I purchaced the bodysuit and painted the whole thing with spray-on fabric paint. It took about 11 or so bottles of that to paint the whole bodysuit. And there are still places where I need to paint more on! The green designs were hand painted.
The helmet is made out of craft foam and posterboard. The designs were painted on with 3D paint and then the whole thing was spray painted. The ears are also made out of craft foam and I just painted the designs on.

Otakon