There are several ways to go ...
Since you have created blogs, I hope you have used WP as the Blog base. If so, it will ping the search engines already automatically every time you post something which is a great plus.
Second you can combine all the rss feeds of the blogs into one rss feed and
1. bookmark them
2. ping them
3. Use a tool such as blogslammer to post the feeds to other blogs
etc ...
Also, even so it became less effective ... create one big directory and ping that every few hours .. eventually the directory will be banned but by then it has fulfilled its use an brought you the spiders ..
You might want to have a look at this http://www.blackhatworld.com/blackhat-seo/making-money/29128-charles-blog-farm-method.html about using WP as a cloaker.