In the case of an atheist, I would think intellectual argumentation might be useful, although like I said, it depends on the person, and I wouldn't rest everything upon intellectual proofs (If I did that, the atheist would think I'm just like him, only stupid). But we must be mindful that study does not replace faith; it merely redirects it. Simply because you think about what you believe doesn't mean you no longer believe. Like I said before, someone may have reason to believe, but it's belief nonetheless.
Like I said before, study does not necessarily replace faith. I have yet to see some sort of adequate form of argumentation fully prove God's existence 100%. I have, however, seen arguments from those who have studied that show it is more reasonable to believe in God than not. Reason then directs someone's faith, but does not replace it. Reason can only go so far, and faith takes you the rest of the way.