I usually use my Clover seam ripper or the one that come with the sewing
machine. The Clover has a a nicer handle. I use an even smaller stitch
length - 1.8 on my Janome 6600. I find it easier if I turn the seam ripper on
the side rather than straight down...the blade is flat against the fabric
instead of perpendicular. See what I mean? And I unstitch every two or
three stitches then pull the thread on the other side. It's very easy.