Is Ruqya a Shia practice? And do we believe that Jinns can possess the bodies of human beings? Or are those who claim to do this con-artists?

Ws it is an ancient religious practice that was used by idol worshipers and others.
After Islam the people replaced the idols by Allah and His attributes and the verses of the holy quran in the Zikr of Ruqyha. The masoomin aa did not condemn such practice on the contrary according to some narrations they taught the people how to do such properly.