You can actually do an empty rebase with:
git rebase --interactive HEAD
Now, just paste in additional hashes that you want to pick:
pick 1efd396b * Fixed a bug in frob function
pick f01934db * Awesome feature added
pick 6fd109c1 * Refactored the widgets layer
squash 3900fd77 * Refactored the widgets layer s'more
To produce the pick lists for this method, use git log --oneline --reverse from..to, then trim the output needed and prepend the rebase commands to each line: pick, squash