Gypsy Jazz is of some use when playing Celtic folk, but not the answer to everything. Hornpipes, jigs etc need a lilty swing, but not off the beat. It's not just the drums that are trying to be clever in most of the available styles. The piano or guitar is also jazzing around. Folk is a pretty simple affair compared to jazz. Reels need an oompah style bass. Chords are not always played complete, so the feature of blocking out parts of the chord is good. I would like to be able to write a moving bass without any chord sometimes. We folkies need less sophisticated backing, to start with!
Do you need any help? I would be happy to provide some examples, in MuseScore/Midi/XML.