Well then the most useful of advice I could give you is to contact directly the founders of countmeout.ie themselves. There is three of them to my knowledge.
They have done media appearances on both Irish Radio and Television and have spoken at several meetings including the AGM of Atheist Ireland. So from a media perspective as well as a knowledge perspective they are experienced and skilled speakers.
They have described themselves as "An atheist, an agnostic and a lapsed Catholic" in the past so they would appear to be just the cross section of people you want, and who better to do your research on than the people who founded the site?
You will find one such talk by one of the founders here:http://www.youtube.com/watch?v=L2HBfNtZefs
I repeat also the recommendation to find the threads, all of which have become very long, on not only this site, but boards.ie and politics.ie on this very subject and are populated by people both in the process and post- process of defection. The one from this site is here:viewtopic.php?f=1&t=2524&start=0
but I will leave you to find them on the other sites yourself.