Have you ever tried to use blender's "Auto weighting" option on a source engine armature?
If you did, you'd notice that pretty much every single bone would need to be fixed, which is a giant pain to do.
I figured out how to rig it automatically so that you only need minimal fixups in a few spots (mostly where edges are split, like neckline, shoes and mouth insides.)

The reason automatic weights never seemed to work is the entire armature setup source engine is using. You should have every tip of a bone touch the base of its child bone. But source engine has their bones sideways, upright and scattered all over the model.

The video below teaches you how to rig your mesh automatically almost perfectly by temporarily making a secondary armature just for rigging.


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