First I had to cut the latex out of the mouth and eyes. Then I took two layers of window screen and hot glued them to the inside of the mask. The second layer is glued on offset to the first layer. A fellow mask aficionado told me of this technique. Thanks Travis!
The nice thing about using hot glue is that if you ever want to take it off, it just peels off and doesn't damage the mask.
Note: Do not use hot glue on the outside of a mask unless it is a mask you don't care about. If you try to peel off the glue it will take paint with it!
Here is how it looks screened. From a distance you won't see the screen, it will look like empty black holes.