You can show up in the bank and get it done on the spot. At least I have never had an issue obtaining a draft, and assuming it isn't for a sizeable sum it should be hassle free.
Alternatively you can show up in the bank and assuming you have your friends bank account details, bank address and their address (needs to be international details so IBAN not their local account number - they can easily obtain this information from their own bank), you can do an international transfer directly to their account there and then. If you pay an additional fee you can get it express, I believe that is up to three days but I have had it turn up the same day (first thing in the morning at a different Irish bank, but it should be pretty similar).
Or if you have online banking you could have added your friend's details and done the international transfer from there, there is details of how this works on the AIB Internet Banking pages.
If you do opt for a sterling draft, I would advise you to send it registered post as it is effectively cash.
If you opt to do an international transfer make sure you have the correct details as otherwise it may either not proceed and you have to try it again or, worse still, it may get sent to the wrong account. The ONLY details, insofar as I know, that they check is that the IBAN is a valid IBAN for that BIC. They don't check that the name of the person you supply is the person who's account it is.