I get asked this question a lot and, to most people’s frustration, I have to say it comes down to experience. A good DJ specializes in two things: song selection and timing. That skill is only learned by DJing an insane amount of hours in front of hundreds of different audiences, observing and understanding what works and, more importantly, what doesn’t.
The sound of blues is predominantly the relationship between the major and minor 3rd, and the tritone. Dorian is perfect for blues music because it blends so well with the pentatonic scale, offering combinations of both. Plus, the distance between the minor 3rd and major 6th present in Dorian is also a tritone!