Yes, I know that Billy Gibbons' guitar parts on Just Got Paid were overdubbed.  I'm sure he played the rhythm part first, then recorded the lead part over it.  
I didn't mean to suggest that he played both parts at the same time.  My point was that it's a measure of his ability that he was able to play both parts so well.  
According to Wikipedia, the ZZ Top lineup of Gibbons, Dusty Hill and Frank Beard played their first gig together at a Knights of Columbus hall in Beaumont, Texas.  Talk about humble beginnings.

has to be the studio version of this.  It's on this album.  Billy Gibbons sounds like Duane Allman and Dickey Betts in one.  
I've said before that this might be the tightest rock rhythm section ever assembled.   Watching the video linked above, all I could think is that they defined the term "loosely tight" (which was also a brilliantly named band from Arizona; unfortunately, they didn't even win the best-named band from Arizona contest, because they had to compete for that title against Billy Clone and the Same, which was without question the best-named band of all time, bar none).