I don't know 100% that I've fixed all my leaks, but I found them by using a thermal imaging camera. If you know a firefighter that can maybe come over and scan your coach from the exterior, you'll likely find the water trail as it will inevitably look "colder" to the thermal camera. It took me a few scans to find the leaks on mine, but by looking at the exterior where I knew the leaks were behind, I was able to see the cold water trail. I have since sealed the potential sources and am now waiting for the next rain to determine if I've fixed them.
If you use the thermal camera, you'll probably want to do it after dark when the outside temperatures have cooled but the inside of the RV and the exterior shell havn't had a chance to fully cool off. Thermal imaging cameras work best when there's a temperature difference instead of when everything is the same temp.