I drove the car through the winter with heavy duty black duct tape over the holes where I had cut the rusty sections out of each rocker.
Now it's coming up to time to sell the Prius, so the repairs have begun!
Before:
After:
Above: shows a metal patch butt-welded into the opening I had cut. I'm no pro welder, and the metal was perty thin in a few places, so I blew a lot of little holes while welding. I epoxied over the holes for a waterproof seal.
Next up: body filler & smoothing.