#1
I am currently using a DVD course to learn some guitar licks called "Speed Kills 3" from Metal Method, and on one exercise, Michael Angelo Batio says "This lick is in a Dorian Blues Scale".
Now, I Fully understand the concept of modes derived from the Major scale, but how would a Dorian Blues Scale be made? I know dorian is the Second Mode from the major scale, so does that mean the Dorian Blues Scale is the second mode of a Blues Scale?

P.S: for those who own this DVD, the exercise i an referring to is exercise 2
#3
The normal blues scale is the minor pentatonic scale played with a 5 and b5, so i would assume that he means the dorian mode with a 5 and b5.

remember to use the 5 and b5, not just the b5, otherwise you have a totally different scale.
#4
I don't own the DVD so I can't say for sure, but it's likely that he's adding the "blue note" to the standard dorian scale, like a combination between the dorian "scale" and the minor pentatonic blues scale. It might look a bit like this: 1 2 b3 4 b5 5 6 b7.

It has nothing to do with modes. The blues scale doesn't have modes of itself, because one of the notes isn't a scale degree, it's simply a passing tone. Plus it's an alteration of the minor pentatonic scale which doesn't really have modes itself because it's a simplification of a parent heptatonic scale.
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea