If your bending the 15th fret, never use your 1st finger, put that behind the finger thats bending the string. So you could be bending the fretted 15 with your 2nd finger and have your 1st finger lightly over the 14th fret of the same string.
Now... make sure your 1st finger (14th fret one) sticks out more than the 15 fret one. So that when you bend the string your 1st finger touches and mutes the bass string first. You can then bend and vibrate the string with the stuck out finger muting the opposing string.
You can see slash doing this all the time, particulary on knockin on heavens door solo on the queen tribute show!