the company I work for uses only threaded ball valves for gas valves, at least in cook-line manifolds. Maybe you could try that? the handles on the ball valves are a lot longer and easier to turn than gas valves or iron body gas stops. That is, if you are allowed to use them by code.
If this is a lubricated plug cock Nordstrum or Rockwell there should be a screw on top that you remove and slide a grease stick inside the the bonnet then screw it in forcing greas around the shutoff body. Check with the supply house for grease sticks.
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