You can use scrapebox to post comments on your own blog, as well as to post content to your own blog.
The Article Scraper Plugin has all tools needed for scraping content, spinning, Quality Assurance, and posting the content to you blogs.
Then you can use the comment poster in scrapebox to post comments on your own blog. Scrapebox even created a plugin that allows you to mass post on your blog and bypass the standard commenting limit. You can post as many comments as you like, and I cover how to make it all auto approve so that you do not need to go in and approve all comments.
You can even build links to your blog when your done.