Watch the Fretting Behind The Slide online guitar lesson by Geoff Hartwell from Guitar Lab: Electric Slide
This is a ground breaking technique pioneered by the great Sonny Landreth. In my opinion, it’s the most important advance in the approach to slide guitar since the first person put slide to string. It was his solution to getting minor notes in a major tuning and vice versa. An added bonus is that you can use it to embellish and color chords of all types. The main secret to this technique is relaxation and finesse. Use your very gentle sense of touch in combination with careful listening to achieve these sounds. Once you understand the concept, it can be a ton of fun trying to apply this to lots of different chords and songs. Check out Sonny Landreth
for more inspiration.