Dear Federico,
I agree 100% the procedure recommended by you, and also I want to share with you:
1. Sources where we get links: Webmaster tools, SEOMoz, and link magestic, so you will get a hughe list of links, so we are working on this list, also google know that the problematic links are usually abandoned blogs (which register the domain only for one year) and in general doesn't provides any contact info, even if you contact the hosting people, in general they say "No response from the owner of this account" ....
So we try to remove the possible, and fill the disavow and comment to Google Team the job done.
At this time you was responding to my question with a 10++
Thank you
PD.: Do you speak spanish ? I'm from Argentina