The hand overcast method might sound self explanatory, but it's not, not really. If you don't do it right, and you don't keep it consistent, you'll find yourself with a seam finish that bunches. Start by ironing your seam open and flat, but use a very low setting. Delicate fabrics don't like a lot of heat. That's one of the many reasons they're labeled 'delicate'.
Once your seam is flat, hand stitch diagonal stitches ⅛" from the raw edge of the seam allowance. Make sure the stitches fall diagonally and that you don't pull too tight. You don't want the fabric bunching. Take your time. You'll want to make sure the stitches are ¼" apart. Keep it consistent. If this is difficult for you, consider pinning a piece of graph paper to the seam allowance as a guide. Even stitches that aren't too tight are the key to this delicate seam finish.
