Modding a survivor is a large process, made up of simple steps. The process isn't just converting from one file format to another. You generally have to edit a mesh, rig, rename files, and run various tools to get a model to work as a survivor in L4D2.

The Table of Contents gives a good outline, but most of it can be summed up in this way:

• 1. Extract the model files you are going to replace.

  2. Match your custom mesh to the mesh of the survivor you are replacing.

  3. Rig the custom mesh to the bones of the survivor you are replacing.

  4. Compile the custom model.

  5. Package the model into an addon for easy use.