Set Alpha for Multiple Materials

If it wasn’t obvious, this question gives me away as a blender noob.

The situation is that I have a single object with ~100 separate materials (created by joining ~100 individual objects that had only one material). This is a model of some real-life geometry, and was imported from a VRML file.

Over the course of the video that I’m making, I’d like the object to fade in and out a couple of times. So far, it looks to me like I’ll have to set the Z Transparency alpha for each material individually, which is super tedious, and this isn’t the only such object I have. Is there a way to select multiple materials and set their alpha all at once?

I feel like this is a pretty simple task, but I’ve spent all day so far wrestling with it, searching the forums, and searching google. Thanks for any help!

3D View:
https://dl.dropboxusercontent.com/u/19765821/Blender01.png
Outliner:
https://dl.dropboxusercontent.com/u/19765821/Blender02.png

Does each separate joined ‘object’ need to have its own unique material ?

Probably not. Is there a way to merge from my ~100 to just 1 material?

In edit mode select all faces (A), select the material you want and press the Assign button in the material panel.
or
Use the Material Utils addon http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/3D%20interaction/Materials%20Utils to assign the material and remove the rest

Excellent! Thanks!