I visited another nearby RV-14 builder for a quick lesson on fluting rib flanges. I had never tried that before, and wanted to make sure I was on the right path. He uses the method shown in this video:
https://www.youtube.com/watch?v=pIvFpVV6kIQ&feature=youtu.be

After a couple of hours in my neighbor's shop, I returned home with straight ribs for the vertical stabilizer. One additional note – my neighbor recommended scuffing the flanges before fluting if you're planning to prime. It's easier to do the initial scuff while the flange is flat than a fluted flange.