What's the right way to add extra gluten to dough?
Making gluten per that video is useful for an experiment but not so useful as a recipe addition. As Steve points out, the right solution here is to buy Vital Wheat Gluten. I buy it in the bulk food section at two local stores (WinCo, Central Market) and I've also seen it in the specialty flours section (usually in a Bob's Red Mill package) at better grocery stores.
Vital wheat gluten is a powder. Just add it to your dry ingredients when making bread. I usually grind my own flour so I know exactly what level of protein and gluten are in my wheat berries. If I'm using hard winter wheat or I want a denser loaf with smaller holes (think: sandwich bread) then I don't add any gluten. If I'm making a whole wheat or mixed grain loaf, then I always add some. For a whole wheat loaf, adding a tablespoon of vital wheat gluten is about right.