Ask as many questions as you want, but don't offer your own opinions. Make them do the talking and shut up except to keep them honest and to give them guilt trips if they try bullying, lying, changing the subject, or any other trickery to avoid answering your questions.
Remember at all times, that you must portray yourself as asking because you want to understand the Truth, not because you are Satan's minion trying to steal their salvation away from them.