The old timer at my Chicago bench taught me to breathe on the shutter blades before touching them
Last month a retired repair guy named Walt came into my Chicago bench with a 1958 rangefinder that had a lazy shutter, and before I grabbed my tools he took the camera, held it close, and breathed warm air across the blades twice. He told me the tiny bit of moisture loosens old oil just enough to test the timing without tearing the whole thing down first, and sure enough the second curtain fired clean at 1/125. Does anyone else here use breath or heat tricks on stubborn leaf shutters, or am I late to something everyone already knows?
Walt's trick works because old oil gets stiff and a little warmth loosens it enough to move. Dry air alone won't do much, you need that moisture. Works on watches too for the same reason. Just don't overdo it or you'll fog the glass and rust the springs. It's a test trick, not a fix.