Creating a 4 bar loop will take a little more thought, and you'll have to execute and record cleanly. You'll want to consider the arrangement and what parts you'll overdub later. I can't stress enough that pre-planning will yield the best results, unless you're a genius.
Let’s take a look at creating a 4 bar loop by expanding upon the 2 bar idea we created in the last segment. Notice that part 1 is rhythmically consistent with the push occurring on the "and" of the 2 beat in each measure. The second guitar part is upper voiced triads that also utilize the pushed 2 beat, but notice there's no downbeat attack to leave a bit more space at the front of each bar. The third guitar part is playing a muted "bubble part" single note line that gracefully outlines the chord changes but also leaves space in the middle of each bar.