a script should not be difficult if all the props have an identifiable name.

something like this should work

 

import poser

scene = poser.Scene()

actors = scene.Actors()

for actor in actors:

   if actor.IsProp() and actor.Name().Startswith("Forest");

       actor.LoadMaterialCollection("/runtime/texture/myfolder/mymaterial.mc6")

print"Done"