How do I find the exact position of a Hartmann line crossing in my bedroom?

I have been experiencing poor sleep for months and suspect geopathic stress. I bought a pair of L-rods but am not sure how to walk the grid systematically. Any tips on technique and confirming findings?

I have read Volume I (Geobiology) and Volume III (Radiesthesia) but would love practical step-by-step guidance from someone who has done it.