If you want to join the Air Corps, you'll have to wait until they advertise cadetships.
As you rightly stated, competition for the cadetships is fierce (2000:1, I believe) and the Air Corps is not keen to spend money training people who are likely to leave at the earliest opportunity. You will be signing up for a minimum of 12 years, which does not include your time as a Cadet.
The process consists of a telephone interview, physical fitness tests, psychometric testing and several face-to-face panel interviews.
You will get bonus points if you successfully finish your degree (10% - well worth having). More bonus points if you are/were in the RDF/FCA (2-3% depending on rank) and even more points if you are prepared to submit to (and pass!) an additional interview
as gaeilge (6-8% I think).
The medical is very stringent and highly specific - tougher than Class 1 standards plus some more unusual military requirements... number and quality of teeth, body and limb measurements, i.e. hip to knee, knee to heel, etc.
If you get through all that, you'll join a combined forces cadet class at the Curragh for
15 months Army Officer Cadet training. After that you go to Bal for basic and advanced flight training, culminating in (hopefully) a commission and a wings ceremony. The washout rate is high, during both Army and flight training.
You are allowed to express a preference for fixed or rotary wing, but you're certainly not guaranteed to get it. I believe that only the highest scoring cadet from each class is allowed an active choice in their assignment. The split (fixed/rotary) will depend on Air Corps requirements at the time and QFI view of your abilities.
Say you follow a fixed-wing path, you will get a long-term assignment which may or may not suit you... and there's not a lot you can do about it. That's military life for you. If you get allocated to the CASAs you will end up flying in circles over the Atlantic seaboard but your hours are likely to be high. Life on the Learjet or G-IV is more varied. Or you could end up flying the Guards around getting very little time!
If you like the military life and flying, the Air Corps offers a unique, rewarding, enjoyable career with opportunities, flying and otherwise, that you simply won't get in the civilian world.
If you don't like military life... it could be
HELL.
If you are interested in going for this, I recommend you check that you meet the medical requirements first, then get yourself as physically fit as possible. You should also join your local RDF unit whilst waiting for the next cadetship competition. The RDF will give you the opportunity to see what military life is like (well, sort of) and shows the selection panel that you're serious about it. If you don't like the RDF, chances are you're going to hate Cadet training.