I admit I haven't done much dowsing with a witness other than baited locator rods but this take on witnesses is worth a read. In case anybody doesn't know, the French were really, really into dowsing. Many of the world's top dowsers from back in the Golden years early 1900's were from France. I realize most people can't read French, me neither, so it hasn't been out there for English speaking people. Of course Christopher Hills was into this big time. He inherited the lifetime works of over 150 dowsers mostly from that area and translated it to English. And it can be seen in his book "Supersensonics" also known as "The Diviner's Bible". Strangely he does not even mention L-rods in the book of over 600 pages. My experience over 40 years is because L-rods are a lot harder to learn than most people realize. Somewhere there is a link to a free copy on this forum. But in the mean time this book on Jacob's rod has some good info.
It's also my strong opinion that much of modern day dowsing is so watered down there is nothing left, much like a homeopathic remedy where literally there is not even one molecule remaining. I really don't like to use the term "Redneck dowsing" because that is an insult to rednecks. It's below that level what people are putting out as legitimate. Don't fall for the easy path, do it right. BTW, my neck a redder than most. Good, hard labor is good for the soul.