I've tried out the perforated aluminum, but all I got was a glass-looking texture. I need a weathered steel/metal/corten curtain wall, i.e. De Young Museum [http://lh3.ggpht.com/-lL8Btl4-SE0/SXOnv6Co59I/AAAAAAAACrw/O5OBwF9qNiU/DSCN2456.JPG], rendered out for a studio project. But I have no idea how to make materials...Any suggestions?

Also - when applying perforated materials, how should I make the masses? I know that 2D surfaces are a no-no, but how do the perforated holes appear on a 3D object?

Sounds like the repetition was too high, leading to sub-pixel features possibly. Try again after tweaking the geometry UVs; you can also change the Rotation/Scale settings in Indigo's texture window for a similar result (when dealing with blend textures that is). For instance instead of :

1 | 0 | 0 | 1
try:
0.01 | 0 | 0 | 0.01

There is this Indigo material called "null" wich does just... nothing. Blended with a metal material it would figure the holes by transparency. It is the method this perforated material is using, only that a procedural shader stands for the blend texture.