Yep. I call it kamikaze counter sinking or dimpling. Free hand can liberate you from the cage
. Just be darn sure you can meet your quality assurance expectations before ruining a part. The other such operation is a dimple die in the rivet gun and it's companion in a backing buck. Do you feel lucky?
<smily face fully implied!>
Once you get over the pressures, angles, and all the ways this could go wrong, you'll be moving right along without so much jig analysis. I know a Boeing production engineer would be squirming in his seat, but we aren't build a space shuttle here.