What Castiel can or can’t do will have to wait for his appearance in the stories, if and when he comes. Can’t be giving away trade secrets, after all 🙂
But as for a new journal and new clothes, Sam has both of these things. In A Schism of Fire and Water, Sam was given a journal from Dean for his birthday (just because it’s made for a dollhouse doesn’t mean it isn’t useful), and Krissy made him new clothing that Walt and the others gave him.
Brothers Apart 