So - here's what I did ... sorry - no pictures of the prep work, I didn't think about a blog post until I actually started sewing.
1. Cut some bias strips (1.5" wide x whatever length you've got - mine were about 15" to start and got shorter, which is NO problem.) Sew the strips together into one really long strip ... make it as long as you need. Press the seams open and fold and press with the raw edges together the entire length of the strip.
2. Machine adjustments ... you'll be using the blind hem stitch - the one that goes straight for a few stitches then swings out for one zigzag, then goes straight again. On my Bernina it's Stitch #9. Make your stitch width as wide as you can and the lenth about 3. You might want to play a little and see how it looks before you commit.
You also need to tighten your tension (a lot). My machine goes 0 -10 and I used a 9.
Now you're ready to sew. Place the fabric strip with the fold to the right. You want the right "swing" of the zigzag to go just off the fabric. The straight stitches will be on the left. My finger is there JUST for contrast ... do NOT sew with your finger in the way!
Here's what the strip will look like after you've sew the length of it. The tight tension is what makes the little scallop along the edge.
Because it's cut on the bias, it can easily be sewn around a curve ... like a neckline or an armhole. Remember to PRESS!
If the garment is not lined or faced, you have to "clean finish" the edge. I use a serger but you can simply do a close zigzag stitch.
Then press, turning the raw edge under.