The only thing I could think of is to copy each of the content into a new post and publish it under a future timestamp to time the release.
there is this Python script called mt-send, you can google it. There are a few others out there and they are all free, however I have not been able to get it to work. . .
I don't know any free scripts, but I would recommend that you use Word-Press-Rewriter. I use it and its great!