Ziv Qual has a great tutorial on CGArena about performing Multi-channel texturing in 3DS Max.

The method I refer to as Multi channel texturing takes advantage of the ability to have many different map channels (in other softwares like Maya this is referred to as UV-sets) for the same object while it’s material is made out of many maps mixed together using masks with these map channels.

In other words – almost the entire texturing process of the character’s armor parts is done within Max through the UV’s using only one material and a few textures.

via Advanced Multi-Channel Texturing – CGArena.