I´d suggest white makeup (liquid would probably be best)--easy enough to find at costume stores or at makeup counters as "goth white" makeup. Underneath the makeup, I´d put silicone (like the one they use to make sake scars and such) as a base to the face; making all those scars will take a while. Also, make sure that you have spirit glue as well to make it stick (though it might stick by itself--I´ve only ever used silicone ears, the scar silicone might stick itself). And spirit glue remover (to avoid unpleasantness when pulling the "scars" off).
So, basically:
1) Lots of silicone for fake scars
2) White face makeup as a base
3) Reddish skintone makeup (I´d actually go with matte eyeshadow powder; easier to find and handle) to do all those highlights around the scarring (and in the "lines" between) and give them that extra "real" look.
You´ll probably take hours, considering what his face looks like.....
EDIT: I completely missed the point there.....I actually bought my silicone ears on EBay, from a store that sells stuff for LARP. You might have some luck searching for that. Oh, and another friend of mine bought her liquid silicone stuff for when she cosplayed the Joker at a theater and costume supplies store. It´s a physical store, and it doesn´t have a website though. :/ Shame.