I’m not quite sure what you’re looking for, but it looks like your wall is basically two solid bodies. One general solution is to double click on the wall, use the loop tool and then extrude towards the other wall. But another method that works for a wide variety of problems is the following :
These roofs are both trapezoidal, so I feel to hard make it this way.
But I found very useful tools and ways from your tutorial!
I’ll try and search more ways.