Create your map.
Select a brush that is not an entity and press n to open the Entity Inspector.
Set the key _celshader and the value cel/ink for the entity.
Compile your map and place the .bsp file in the maps directory in your .pk3!
Type \devmap mapname (=.bsp filename) into the console.
Finished. Now you'll notice the black texture that occurs at edges.
Example map: AMT-Run2
Note: If you use the cel shader, you will get higher r_speeds!
Important: Be sure that the cel.shader file is in your scripts directory and you have updated the shaderlist.txt. The cel.shader is included in Q3Map2\extras\cel.shader.