"Washing charcoal" in Chaozhou dialect is actually poking fun at a social role, that is, the so-called "entrustment" or "childcare". In the past, when people on the tramp set up stalls to sell medicines, there was often a person boasting about how amazing his family's ancestral medical skills were and how many patients were cured, such as Zhang Si and so on. Another man asked them to follow him and make a scene with his words. In addition, they may mix in the crowd to take the lead in applauding and buying medicine.
Exodus: Those who say that medicine has magical effects are all hired by drug sellers to wash charcoal, and they are all cheated.