I think the stitch that Mkotch is referring to is a blind hem stitch. It's what I use rather than a zigzag or straight outline.
Just be aware that even though the thread is almost invisible the large needle leaves a large hole, not so bad on some fabrics but really noticeable on tighter weaves like batiks.
I sometimes use the darker and the clear IV thread in the same piece, switching when the thread itself shows more than I like.