There is no such thing as a "dofollow" link. A link is either nofollowed, or it's not. IMHO, links that have nofollow are not any worse than links that don't. Google follows them either way. Also, IMHO, the only value gained from going around commenting in various blogs just for the backlinks is that of being labeled a spammer. :-/
Getting dofollow blogs list is not a big deal at all! But before posting comment in any blog it's better to ensure whether your links will be followed by search engines. Actually dofollow and nofollow make huge misconception, there are so many blogs that are nofollow but still can be useful for getting quality traffic to your website.