I spent a lot of time in my youth wearing out flamenco guitar records. Two artists that I listened to the most were Sabicas and Manitas de Plata. They played a kind of long nailed progressive and popular form of flamenco guitar in the 60s, and they pioneered playing flamenco music as a solo music that could stand on its own.
Although I've never truly played flamenco music myself, I've copped an awful lot of licks from these guys. Until YouTube came along, I never had a chance to actually see them play. I recommend that every guitar player should take a look at their form and technique. If you're a fingerstyle player, look at the flexibility in the joints of their fingers and see their use of backstrokes. Finger pickers tend to have stiff fingers, but these guys are loose.
I've included some other famous flamenco guitar players of the 20th century. You can compare the subtle differences in technique they employ. You'll notice that Manitas de Plata is playing a form of flamenco rumba -- that is he's taking a Cuban rhythm and making it flamenco. This kind of music became very popular in Spain and still is.