Watch the Johnny: Ex. 4a online guitar lesson by Andy Aledort from Kings of Rock & Roll Vol. 1: Johnny Winter

Johnny Winter is a master slide guitarist, and his cover version of the Bob Dylan classic "Highway 61" is a tour-de-force of modern electric slide; it has influenced countless guitarists since its release in 1969 on Second Winter.
Johnny usually plays slide in an "open" tuning (strumming across the unfretted strings produces the sound of a chord), and this excerpt is played in an open D tuning (D A D F# A D) that he utilized occasionally. While I use a glass "Coricidin" style slide on my ring finger, Johnny prefers a metal slide made of conduit pipe worn on the pinkie.