Just another thought on how to find good blogs to comment on: Google for some blogs in your niche. I find it helps if you include "keywordluv" or "commentluv" in your search because you know that you can leave your URL in the comment field. Also, a fair proportion of these will be dofollow. (Of course it's not vital that every blog you comment on is dofollow. In fact, you can get much greater benefits in the long run from good nofollow blogs, particularly if the blogger likes what you have written and links to one of your posts. That said, it's nice when a blog is dofollow, since you know that you are getting some direct search engine benefit from the post itself.)
Do this, and you're sure to find some good, busy blogs in your niche, with lots of comments. Isolate the ones with the most recent posts, then click on the individual posts. Logic dictates that the best commenters will also have the best blogs. So, just scroll down and look for the best comments. And click on their blogs!
Then do the same thing all over again with each quality, comment rich blog you find. If you get on a roll with this, it's possible to find dozens of new blogs this way without once having to return to Google to restart your search.