A boarding card for the DUB-CFN flight isn't necessary. If you've got it great, but you might be outside the time limit (no idea what BE does). Having your e-ticket printed out showing an OK status is just as good.
If '1st airline' accepts bags through to CFN that will be shown on your baggage receipt. The tag on the bag should have CFN on it, as well as all the other connecting points in sequential order. If it only says DUB that's where the bag will end up. If it says DUB and CFN then the bag will go through to CFN.
I'm not sure how the Irish do it. You may have to clear immigration and customs at your first point of entry. If so, and regardless of where the bag is tagged to, you will have to clear immigration, pick up your bag, clear customs and then either give the already tagged bag to CFN to the airline - or if it's only tagged to DUB you will have to check-in the bag with the local operator. (Is it really BE?)
Last edited by ExXB; 18th Sep 2013 at 11:27.