Watch the Billy Gibbons online guitar lesson by Jeff McErlain from Kings of Tone
Billy should hold a patent on this technique! Certainly he did not invent them but that has become a definable element of his sound. The technique takes a little while to get down but keep at it. Usually you get one to ring out and then you have the feel of how to do it. Other pick squeal kings: Eddie Van Halen and Zakk Wylde.