Give it a try! I re-watched that section and can’t think of where a bridge would be helpful, but I could be missing something.
Shear is awesome! It creates an angle while keeping the vertices in their horizontal axis. Here’s another example of it at work: https://youtu.be/VC89Qfw9pkg?t=252
Doubles, overlapping vertices, can be caused by quite a lot of things! Most often cause for beginners is extruding or duplicating something and then hitting Esc, which cancels the movement but not the added geometry. More on that in the Mesh Modeling Bootcamp: https://cgcookie.com/course/mesh-modeling-bootcamp
