I suspect that as Poser isn't listing the materials for the parented props, you'll need to make seperate MC6s for each prop and the figure they're parented to.
Why, because the material room only has one selected item and will either ignore any materials not present on that item or create new and useless entries which have no affect (which was the previous behaviour, PPro may have changed it).

Attempting to make a MAT pose would run you into all the problems normally associated with pose, props and naming.

The best solution would be to write a Wacro to apply the MC6s to the appropriate props, which is called from the MC6 for the figure.