Here are three MAT tutorals that can be linked to thru the Renderosity tutorial Poser section

http://www.renderosity.com/~syyd/pntuts/mat.htm

http://www.fallencity.net/lore/poser-mat-creation.php

And the one that seems to be the easiest to do (at least for my mentality L) - http://dragonayerie.topcities.com/creating_matt_poses.htm

All these by very talented & generous Renderosity folk - hope they're what you were looking for. :)