I have taken out machine quilting. I am very new to longarm quilting and I tried to do some fancy stuff on one of my "good" quilts. It was so bad that I took it off the frame and starting "skinning" it. I use a razor blade and cut the stitches between the batting and the backing. If I get a cut in the backing, that's fine.
As for how long it takes? I'll have to let you know when I finish skinning it. :D