This is really not difficult; particularly on circulars where the stitches are resting on the cable with room to spare to slide the tapestry needle through. You can gather quite a few stitches at one time on the tapestry needle and then pull it through. With 400 stitches per row it takes less than 10 minutes to run a line through the entire set of stitches. I use embroidery floss because it is slippery and glides through easily; also I can use just 2 or 3 of the threads in the floss if the stitches are really tiny.Coral McRae said:
Also, choose a row to run the lifeline through which is composed of all knit or all purl stitches if at all possible. They are much easier to pick up than YOs, incs, decs. A steel needle works much easier than a plastic one; they are available at JoAnn's, sometimes in sets of upholstery needles if not available separately.