I have noticed that a lot of fiddlers play these unison notes with there 3rd finger with quite an aggressive slide up to the unison. I've always used my 4th finger with a more subtle slide.

How does everybody else play them ?

On the same subject Gina Le Faux does a brilliant version of Jacksons Reel (the one in D not the Em one) with fingered drones through most of the tune - the 4th finger is held down while the tune is played on the next string.