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A Disallow: directive in the robots.txt is not necessarily going to get them removed from Google's index any time soon. It will simply mean that they will no longer crawl them. A meta robots noindex would get them removed but does not seem appropriate since there are so many.
We have dropped the 301 redirects because somehow google has managed to get into this mess
When used in conjunction with the removal tool, it's immediate ... You either have to put a block in the robots.txt or a noindex on the pages to use the tool successfully.