The process for getting money back is usually fairly simple and there are no questions asked so you can ask for money back for Saturdays, etc even if you don't normally travel on that day.
That being said, the level of compensation is usually inadequate since alternative modes of travel are always more expensive than the journey Irish Rail fail to deliver. For people on point-to-points, a train refund doesn't come close to covering the cost of a bus ticket let alone fuel and tolls for a drive to Dublin.
In the past I've always ended up out of pocket after Irish Rail strikes and having to suffer longer uncomfortable journeys. Nobody seems to care at all about this - one can understand the commuter having to suffer so that the train drivers can enjoy higher pay but it is difficult to see why they should have to pay more to get to work.