After some googling I found out that people use bread to erase charcoal. Seems like a massive waste of food, but I guess that's why he made the analogy.
Based on the googling I did to make sure I wasn't translating the line as nonsense, yeah. Apparently that's a main thing artists used to use before rubber erasers became commonplace. Even though rubber erasers were invented in the mid 1700s, I imagine Japan was behind just like they were with a lot of things.