You’ll probably have to remove the Masthead Fitting (truck), to access the inside of the mast. Having dine so, you could probably just use a couple of tie-0wraps to cupport trhe cable.
Use the Wire Mesh Pulling Grip to fish
the wires up the mast.
Then, use a pumping action to “walk” the grip over the cable by bringing your hands together and then relaxing them until the end of the cable protrudes far enough through the throat of the grip* to reach from the point of exit & fastening, to the mast-top device.
The “Chinese Finger Cuff” strain-relief grip is also known as a Pulling Sock, Basket, or Kellems grip.