Here I am with another question about Paint Effects.

I read a lot about ZDepht issues and converting PFX strokes to polygons both on the docs and on the forums around.

But I didn't found nothing about creating a MATTE shader within this context: Paint Effects Objects and Maya Software.
I want to use Paint Effects Objects and render with maya software, but also I want to be able to create render layers for my elements: big tree, little tree, and grass. All with a trasparent background, as I am willing to add the background later within After Effects.
I suppose the typical solution when using mental Ray and/or PFX objects converted to Polys is to assign a [Surface Shader] and turn [Out Matte Opacity] to 100% black.

I tried assigning a Surface Shader to a Paint Effects Object, but it doesn't seem to work.
I also tried to set to 100% black all of the Paint Effects Object shading attributes (color1 and 2, incandescence1 and 2, tranparency and so on), but that really didn't work as a MATTE shader.

Sorry if it is a dumb question, but I wasn't able to understand it just by reading the docs or searching through the forums.

Thanks!