In my experience, when you get the glazed eyes, you have gone too far.
You need to get your point across in as few words as possible and then shut up. Don't ever talk about another religious topic that day. They have to think about that one. Make it a good one.
Don't try to tell them anything. You were trained not to listen. So were they.
You were all taught that you had all the answers, so ask a question in such a way that they really want to answer you, then shut up. Don't let them rephrase the question before they answer it. The primary defence is to change the subject.
Whenever a JW answers your question, ask yourself, before you reply, did they really answer my question? They usually haven't. Don't let them get away with it. Act offended that they should use whatever tactic they just tried on you, their friend, father, son, daughter whatever. Take control. Restate your question.
If they make a statement that you know is untrue, put pressure on them to prove it. If you know of a WT article that contradicts them, make them read it to you and explain it to you. You keep your mouth shut. Make them do the talking.
You don't have to 'win'. You only have to make them think.
Cheers
Chris