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:

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.
Use the Material Utils addon to assign the material and remove the rest

Excellent! Thanks!