my friend has a book (can not remember the title or author) that explains how to do this on lots of quilts. I almost always have a few seams with a "twist"--as much from carelessness as not knowing which direction they should be going--starch or steam will lay them down pretty flat. Pressing open means SID is out--but sometimes I do that if I have lots of seams meeting (like with a star, etc). And I have a rubber mallet that I use with a board (and some spray starch) to flatten those that would end up as knots when quilted--works fine.