How to I make materials fade into other materials?

Ok, unfortunately I dont have any examples of what I’m trying to accomplish but I’ll try to explain it the best I can.

Basically I’m trying to make materials fade into other materials. What I mean by that is for example, say you have a battle axe. One texture slot for the color, one texture slot for the greyscale displacement map, etc etc.
But say you want it to look metal, but the segments of the axe that are dirty wont look all reflective and metallic because the dirt stains will hide its metal material. So is there a way to etablish that kind of effect? In that example it would be to fade the shiny reflective metal into a material thats dirty and not very shiny or reflective at all.

Hope this makes a little bit of sense lol.

but I appreciate any help anybody can throw my way. thanks.:D:D:D

The example you mentioned could probably be done better with nodes, but I think stencil is what you are looking for:-

On a similar note, does anyone know if the blenderart Node Cookbook was ever released ?