If there's one thing a sewer has to learn early and often is how to take out a seam. When I worked in stage costume I think we spent more time taking things apart than putting them together. I have used the same tool for 40 years to accomplish this task and I have taken some teasing. I use a very small folding knife or pocket knife, and it is sometimes called a tuxedo knife. I keep the blade sharp so I can slide it under a single stitch every 5 stitches or so and the pull thread from the opposite side and it all comes out quickly. On heavier fabrics I can run the blade between the layers and just slice the thread. This takes a little practice and a sharp blade so that you don't nick the fabric. I also use it the usual way just nicking threads as I spread the fabric. I find traditional seam rippers to be dull and too big to get under stitches. This method has saved me a lot of frustration and time. I can take down a garment completely in less than an hour, and re use parts for redesign. Check a hardware store for the tiniest folding knife and keep it sharp with your cooking cutlery "straightener". Call me crazy but this works better than anything else I have tried.