Costume glow

Simple answer: you can't.
You should to change shader of material and I dont know any easy way to do this. Also you can unpack costume textures and set glow texture to black.
How can I do that? Unpack the costume textures?
Right way is to clone costume what you want. See step 2 here. You'll got folder with costume files, after unpack str2(cm prefix means costume male, cf means costume female) archives and there you get your cpeg textures. Then convert it to dds by this tool. Sufix _gl means glow. Edit texture - convert to cpeg - pack str2 archive - update asm - pack your mod with Workshop upload tool and save it in mods\ directory
But there is more simple but dirty trick by using texmod\umod tool. IDK how they work with SR but if they work than you can grab texture from the memory and edit it directly