Several different ways to use L-rods. I like to walk around the perimeter with one rod pointing off to my side. The GDI-detectors video shows holding two rods a foot apart and doing a”double sweep”. My version is to push my hands together and clamp my left thumb to hold the rod immobile and do a sweep while watching the dead rodJust aim with it as yo do the sweep but most important is to NOT watch the right rod. Your conscious attention to the moveable right rod will destroy any chance you have for success. Some people just can;t help but cheat here, like Lott’s wife, she was told not to look back but she did anyway. My guess 99% of all failed dowagers cannot get past this. When the left rod is aimed at the target the right rod will start to move. Take your mark, then move over a ways and repeat.
Since I am tying as I think just another thought on the first technique. The Box-in method you walk the perimeter with both rods pointing ahead and watch for a response when you are 90 degrees from the target. While this is a tried and true method I prefer aiming the rod off to my side. It is much more sensitive for me.