Hello brycetech , 
 if im following you correctly you want to import a poser animation , and render out a regular color render , and a seperate mask render. 
There are allot of ways to accomplish what you want.
 If you need to reset shaders it in Carrara to all white , first set default shader to the color white you want. Than go to shaders tab and highlight shift click all the shaders you want to be white , on pz3 characters its all 20+ domains are one group. even so heck even 200+ seperate shaders only takes a minute to shift click .... Anyway hit the delete key. Up comes a question , replace masters with default check the yes for all box. Balm a second later everything you picked is your default white. 
 Or can't you just export a all white version from poser using the python script to set all materials as white ? Or just do a search and replace with a text edit program like ultra edit  , that is fast and flexable on the pz3. save two copies color and mask pz3. This avoids having to manually drop these hundreds of shaders in carrara.
 Another  way I make fast but quality mats is just use a bright background color , red,  blue or green whatever works best not to mix to with my colored object. Take that footage to my video edit  program , pick my bright backdrop color and define it as my mask , or mat. Than I can define mask fring or blur , whatever else , and export what I need. The objects themselves are easly cut from the blue red or green . Of course you can invert that and color replace as well to make black and white alphas.
  If I want alpha or masks I try to plan the project first and make 2 versions required for rendering. :)