That's a nice find to be able to buy those little bracket sections - cutting those small pieces to anchor angle structure is a PITA to do quickly with a hacksaw and is dangerous with a circular saw.
After my last build I got smart and took a sacrificial piece of 2x3 and went through drilling the holes on each side of the angle then drove a screw through the angle into the wood so when cut the angle didn't get caught in the saw and jam or go shooting out. Time consuming but at least the cuts come out nicely and the drill holes are evenly spaced. One of the few things I've gotten done to date with the 16'...
For all the time I spent on it though I wish I'd just ordered 50 of them and been done with it.