Looking great dude, keep it up! For the weathering, personally I put a layer of silver paint chipping on edges in different places where it would make sense over the piece, and then a blackwash overtop of it to help blend the chips better, but everyone does it differently. It's your project, so build and mould it to your heart's desire and in whichever way you'd like! Quick question, are you planning on sanding the helmet down or keeping it as is?