@zwantedone Previous discussion can be found here:
http://bluesguitarunleashed.com/forum/index.php?threads/griffs-trading-fours-course.25220/
Prior to each jam Griff explains the scales and patterns he's going to use.
You will trade off every 4 bars.
As he plays the first 4 bars you are
listening and watching so you can play something "similar" for the next 4.
You won't play exactly the same thing, because you will be at a different place in the progression.
(Or maybe you can play exactly the same thing, depending on what he plays.)
Then he'll be playing the V and the turnaround for the last 4 in the first chorus and you'll actually be starting the next one.
It's kind of weird because his parts are already all recorded and you follow him regardless of the position in the progression.
That's the "solving musical problems" he talks about in the intro and "...that's all part of the fun."
So you always follow him, trading off every 4 bars, and you try to play something that "makes sense" based on what he plays, your prior knowledge and where you are in the progression.
Afterward, if you want to go back and see exactly what he played, he has provided transcriptions.