You find the CI results on the existing PR; they'll be displayed there. You just need to make sure that a branch in the repo has the exact same commit ID when you push it as the PR has. (Statuses are reported on commits, and triggered on pushes, so everything should just line up.)
As far as further reviews - on the existing PR too, same as usual.
You will need to run the script again when the contributor pushes their response to a review. One feature that would be useful is to not need to specify the branch name twice, but if you name the second pr_as_branch invocation differently, it just means one more branch that should be deleted when looking at git branch --merged.
-glyph