At a quilt show, I found an electric seam ripper (by Wahl) which works well in undoing seams. It looks like a hair clipper except it is smaller and is an inch wide...one of the best notions I have ever bought. It is held just so that it touches the thread only and the job is done before you know it. I took it to a quilt retreat, and I was helping rip stitches for others
. MSQC sells a different brand, same thing.