Learning the blues...well, it not that simple by just watching a DVD, I believe. Perhaps, some technique is gained by it, but I don't think for blues it is all that important. I believe, expressing that certain bluesy feeling is the key here. The funny thing is, though, you don't really know it until you get there.
For example, if you happen to watch some of these old blues guys, you will notice that most them don't really use the guitar as the primary instrument...it's more what they talk about and the guitar kind of just punctuates their sentences. Now, if one wants to play an all fingerstyle blues, it can become difficult to convey a storyline, a feeling, if you will, unless, if one considers nice technique and chops to be enough, I'm sure there are people who would enjoy just that too.
That said, to really play the blues, one must listen very closely to those who, basically, developed this style of music. Oh...and I would suggest, when getting into to the blues, think of simplicity, don't get too fancy.
...just my thoughts on the subject, like it or not.
