The "double bend" you refer to is relatively simple. You have strike the G and B strings one after another very quickly. It's easiest to play that part using 3 fingers. You would use your ring finger to depress the B string at the 15th fret. You would then use your middle finger to bend the G string at the 14th fret all the way up one full step (to 16th). Additionally you would want to use your index finger to mute the D string to prevent a "clash" of the 2 strings.
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