Dear Sun, I just read the sintua post (i have used to visited the forum a few times becos of a friend who gave me the link), and I have this to say, hope you do not feel offended.
As some of them suggested, it is impossible to 'jump' Buddha. Neither is it possible to jump Guan Yin, Di zhang wang, any other buddhist saints - including Ji Gong! Because Ji Gong is also an enlightened arhants, he has been liberated from the Triple Worlds, and no longer takes reincarnation. He abides in Nirvana, he does not stay in the world. Buddhas and Bodhisattvas also do
NOT deal with spirit mediums and jump on them.
What mediums deal with are really, spirits or spirit-deities (gui shen). Meaning these beings are belonging to the spirit realm. I understand many mediums claim to be able to 'jump' ji gong, or even buddha, bodhidharma, all these enlightened beings. It is impossible

They did jump on another being, but they can simply anyhow claim to jump a particular person, but it does not have to be him. Meaning they are jumping on spirits, or spirit-deities, but not the ones they claimed to be jumping.