I don’t think irish music has been discussed so much here. However I do think this is an interesting subject as some of the rhythms imply some specific things for the right hand, especially how banjo players do it.
I can think of two things:
-the frequent use of triplets (which are actually not triplets but 32th notes)
-and the jig pattern
In both cases, they use a Down Up Down pattern.
“Triplets” in a reel (4/4) would be : D U DuD D U D U D U DuD D U etc… With the 1 and 3.
In a jig (6/8), the basic pattern to make it sound right is: DuD DuD DuD DuD… Here also, always with a downstroke on the 1
(and the jig triplet would be : DuD DuD Dudu DuD
So they commonly have to deal with two downstroke in a row.
Here is a video with a good close up on the picking hand (I fear my explanations are not the best):
At the very beginning, a reel with “triplets”
At 2.15, the jig pattern