Different damage decals for different parts of the model

Let's say I have a cyborg character, where large portions of the anatomy are made of metal. Obviously, I want the flesh parts to display blood decals when shot, whereas the metallic parts should show a different decal (or even NO decal). Do I use two different textures, with different damage properties? Or do I achieve this effect using the hitboxes somehow?

Thanks in advance, cousins.

edit: I suppose if the metal parts are invulnerable, I could achieve this by leaving those parts without any hitboxes. But I'm not sure if that's really what I want.

i'd say different hitboxes, theres no way to check what the face of model you hit's texture. models tend to have 1 surface property so your going to have to overide that based on hitbox.

[wisemx]

Let's hope Valve provides one of the TFC characters in the SDK update.
Several of them exhibit this now.
Notice for example the bounding areas for the Heavy and it's weapon.