I've been working on learning mandolin on-and-off for a few years. Mostly off. I've just picked it up again. My background includes Highland Bagpipes (i.e., Scottish, not ITM). My wife, a good violinist, has been working on fiddle, on-and-off, for decades. Since she retired, fiddle is getting more emphasis.
I play whistle and Scottish Smallpipes, and on some tunes she's written parts to accompany me. It's cool. We're /not/ trying to do Irish session playing. I feel like I need to repeat that because some people will probably feel compelled to learn me on authentic Irish session playing, even though I have no interest

What I do want to do is learn how to accompany fiddle tunes on mandolin.
I'm also learning to play Led Zep's Battle of Evermore. Funny thing: on the internet you can find any number of people who have figured out pretty detailed transcriptions. They've even transcribed and learned to play the tape-delay effect.
Anyway, if anyone has any good resources or advice for learning to accompany Irish and Scottish tunes on Mandolin (i.e., devising arrangements, not session playing), please share.