My biggest block when it came to "sounding like an Irish fiddler" in the early days was rhythm, and probably phrasing to some extent as well. I could play the notes and feel my way through the ornaments from the classical world, but the actual groove and lilt was lacking.
So the exercise that ended up helping me the most was the "reset moment".
Basically you start playing a reel rhythm (or jig or hornpipe -- whichever you need work on) just on one note. It can be the start note of your tune to make it easy. Once you're locked in and in a groove, you start playing the tune.
The moment you feel like you're getting out of the groove you go back to hanging on one note until you're back in.
Rinse and repeat as often as needed! Eventually you'll find you don't have to stop and start so much, and that rhythm comes more naturally to you.
Now that I write this, that's probably going to end up as a video tutorial on my YouTube channel as part of that 100 day experiment soon...! So you'll get a visual and audio aspect of this as well!
I'll be "out of the office" all week teaching at Summer Wheat in mid-Michigan (so you may or may not hear from me next Sunday), but if you're curious in either starting up private lessons in late June/early July or want to check out the video feedback trade option (recorded on your own time like a private lesson, but not live), let me know!
Happy practicing!
~Hannah