The automatic writings of the Irish medium Geraldine Cummins were analyzed by psychical researchers in the 1960s and they revealed that she worked as a cataloguer at the National Library of Ireland and took information from various books that would appear in her automatic writings about ancient history.
They instead use “mental mediumship” tactics like cold reading or gleaning information from sitters before hand (hot reading)
For moderate success as a medium, you also require a good understanding of Chinese culture and society. You need to know who is in the Chinese pantheon, how human problems may be caused by supernatural forces, and what steps can be taken to solve them in the framework of exorcism or other supernaturalism. You need to understand the social structure in which your clients are engaged, and have a grasp of the kinds of drives and motives that produce their opinions and their behavior. You need to be able, in other words, to make an accurate analysis of a client's problem and to propose a realistic way of dealing with it at the same time that you explain his problem to him using symbols that he can understand and that he is motivated to find credible and to accept.
Far more common than being the resident medium of a temple is for a tâng-ki to hang his own shingle and seek a clientele either among friends and neighbors or more widely. In most instances the tâng-ki seems to serve a particular small ward of the city, and some come to be universally respected on their own streets and a few adjacent streets. In other cases, although he may attract some of his clients from his immediate neighborhood, local belief is not by any means universal, or the tâng-ki's ambitions are wider, and his most important recruitment seems to come from a larger area.