Debate: Factory service manuals vs learning by feel, which actually wins?

Had a chat last week with a retired tech from Denver who swore he never opened a manual after 1985. He fixed a sticky shutter on a Pentax K1000 by tapping the body with a screwdriver handle, no disassembly. Meanwhile I spent 3 hours tracing a circuit diagram for the same issue and still needed a part swap. He says modern repairers overthink, but I think his method misses the precision needed for newer electronic cameras. For those of you doing this daily, do you lean on official specs from places like Micro-Tools or trust muscle memory from years of jobs? Has anyone else hit a wall where one approach just stopped making sense?