There is a misunderstanding that the only way to add materials to XPression is one-at-a-time, via the Material Manager. Did you know you can bring in a bunch of materials into the Material Manager all at once? Dragging them onto the Viewport, will add them to the existing scene, as well as place them onto a Quad. They also get added to the Material Manager using the file name they have in the local file system. Watch this, and give it a try.