Second in the series of "quickies" done before turning the laptop in. In all honesty, the fasted way to get a cover accomplished is obviously as an acoustic strum and sing number, but it's not just playing and singing the thing straight through. That gets better results but typically takes at least five takes before I settle into the tune and play it all the way through without any major mistakes. It's much easier to play the guitar in one take, and then record the vocal in one take. It doesn't necessarily always sound inspired, but in a pinch it gets the job done.
Even then, it's a bit difficult to get myself to leave it alone, but sometimes you just have to.