The weeds are finally starting to discolor and shrivel, and I spent half an hour tracking down and spot-spraying glyphosate on any Bermuda grass sprouts I could find. I even found a pine seedling, probably left from all the pine needles, cones, and other debris that I used to compost before the neighbors removed their overgrown trees.
I forgot to turn off the sprinkler system for the required 48 hours, which washed off the herbicide. So I had to spray again. I was so focused on getting the dosage I forgot that many herbicides are slow to penetrate the leaves.
The buffalo grass is mostly thriving. Most of the plugs are much denser, and runners are zooming out in all directions. They seem to have a built-in moisture detector, because the plugs along the edge of the sprinkled area are sending more runners towards the wet dirt than the dry dirt.
About 5% of the plugs are alive but not sending out new leaves or runners. It they don't start doing something soon the more vigorous ones will run over them.