I use a plane on a different render layer to mask out the character. The result comes out quite nice:
EXCEPT for the mask for the eye glowing effect (I duplicate the eye mesh to a different object on a different layer in order to have only the eye glowing, not with the armor (got a glossy shader) glowing too). As you can see, half the eye is still visible despite of I masked that out. It works for the glowing part, though:
Thanks for reading!