Ornamentation is generally a bit more sparse in Sliabh Luachra polkas and slides, for sure. I also think that playing with lift and lilt, indefinable unless you listen to players who possess it and emulate them, is a sine qua non. Ornamentation obviously depends not just on you but also on your instrument, but I wouldn't relegate it to secondary importance. Again, you learn to do it your own way by listening to those who have got the knack. Try Matt Molloy on flute and Noel Hill on concertina (I haven't got any of your records, Dick...), and Jackie Daly on button accordeon. Kevin Burke on fiddle is a great example of a player who is effective yet restrained with ornamentation. There are so many things you simply can't learn from the notes in a tune book. I gave all mine away many years ago, and in my misspent youth I had lots of 'em...