I'm going to be cosplaying Sober!Gamzee later this year at a con. I already have most of the stuff such as the makeup and wig etc , but I'm not sure what to do about his scratches. For those who don't know the character , here's a reference picture: http://images3.wikia.nocookie.net/__...akara_Sane.png
I would research wound makeup. Halloween tutorials are a good resource for this; check YouTube and deviantArt. You may have to do the scratches before painting the rest of your face. Hope this sends you in the right direction. Good luck!