There is no single "traditional style" for Irish flute playing, though one specific style has been heavily promoted as The One True Way in recent decades. Listen to older recordings for a wider variety of ideas.

For chromatic notes, you need to experiment rather than depend on fingering charts, as every instrument is different and you may also need to adjust to the tuning scheme used by whoever you're playing with (equal temperament for a melodeonist, just intonation for a singer, maybe Pythagorean for a harpist). In particular you don't necessarily need to use all the keys you've got - as Paul said, you can often crossfinger the C natural to better effect.