Deception is a common theme. The quack healer is often pretending to have skills they don't really possess. Another theme could be the gullibility of the public. They fall for the quack's false promises easily.
One such novel could be 'The Alchemist' which, in a sense, has elements of a quack healer's journey as the main character Santiago embarks on a seemingly quixotic pursuit of his 'Personal Legend' which involves learning about alchemy and spiritual healing. However, it's a very metaphorical take on the idea.
The sound of cawing could be described with words. The following words can be used to describe the sound of quacking: quack, quack. These words were all onomatopoeic words used to simulate the sounds of ducks, geese, and other animals.
You could focus on developing skills or powers that are not typically associated with healing. Maybe have a character specialize in combat or magic that isn't related to restoration.
You can try looking on popular manga reading websites like MangaDex or MangaFox. They often have a wide range of manga available, including Redo of Healer.
Bai Jingting had performed the quack quack dance in some videos. In these videos, his dance moves would sometimes be interrupted or he would feel embarrassed. Although there was no specific teaching or detailed description, it was certain that Bai Jingting had indeed danced the quack.