The video is correct - you just solder wires from the pins to replace the traces. Your board is a little different as it has two switches connected to each diode but it's the same theory.
For left ctrl the pin nearest the corner goes to the matching pin of the switch next to it, the other pin goes to the right leg of D50.
The right one isn't so obvious but the pin that's not near the edge goes to the right leg of D56. The other trace goes off the edge one end of your pic and disappears through a via the other end so you'll need to post a bigger area, or just follow the trace past the arrows until it hits another switch. Doesn't matter how long the wire is it will still work.