Watch the Swing It On Over online guitar lesson by David Blacker from Swing Blues Survival Guide: Lead
In the first couple measures of this piece we have some great interplay between major and dominant sounds. When you listen to great country pickers like Albert Lee, you hear this awesome tapestry of major, dominant, and minor pentatonic sounds. Being able to fluidly move between these ideas is a key take-away from this piece.
Leading into the IV chord, you have some nice chromatic runs in E blues. That chromaticism is another key element here. You'll notice that for a country/western feel, it sounds right to lead into the IV chord by ending the 4th measure with the root note of E (14th fret D string). Of course there are no rules, but I have been hammering home the idea of setting up the change to the IV with a dominant 7 sound, so I wanted to point this out.
For the IV chord change, locate the IV chord shape with the root on the 12th fret of the A string, major 3rd on the 11th fret of the D string, and the 5th on the 9th fret of the G string. That's the shape these IV chord licks fall off of. Notice that the turnaround begins by outlining a B major chord, and then implies a change to the IV (to create movement) while the backing track stays on the V.