Standard Tuning. Works best with a bit of fuzzy overdrive, 
compression up high enough that it lightly squishes the initial attack, 
and a quick slapback delay with one repeat. Listen to the song to get a feel for it. The chord
that he's using on the G and B strings is this:
|
|      6
|barre 5 
|      5 
|
|
He's using a new Dr. Z DB4 with some grit and I was able to get it with the Wampler Paisley Drive
and Ego Compressor(which Brad uses) and the Wampler Faux Tape Echo set with one repeat.


The first slide is just for the intro, Brad uses hammer-on's after that.
Please refer to 1:28 in this video for the easiest way to fret it: 
https://www.youtube.com/watch?v=HgnCoj0OYcA

~ Very light vibrato
/ - Slide up neck
\ - slide down neck



Repeat this for the verses of the song as well.

      Slide                 							
|-------------------------------------------------------------------------------
|-------------------------------------------------6-------------6--6/8--6-------
|------------5-----------------5-------------5----5---5----5----5--7/9--7p5-----
|------5/7---5---7\----5-h-7---5---7~---5----5h7------7----5h7---------------7--
|------5/7-------7\----5-h-7-------7~---5---------------------------------------
|-------------------------------------------------------------------------------
					     (Let the 6 on the B string ring open)