A lot of blues comes from technique anyway... Bends, vibrato, sustained notes. I know exactly where you're coming from. I would say take the major scale and work around with it. Music theory is a guide... not a rule book. Play what sounds good. I like to take the Slash approach to playing guitar. It doesn't matter if it's in the right key as long as it sounds good. As long as you can find the root notes you should be able to figure out real quick which notes go with it or not. Sometimes I will jam out and just play notes and people will ask what scale I was playing becuase they liked the way it sounded... Usually I would say... I don't even know. Another thing you can do is get a large scale book like the Guitar Grimoire and look for some scales in there that might go with major scales but give it more of a pentatonic/bluesy feel. Just play.