With the exception of 2 babies that are in a very low wind site all my machines have had a manual shut down. I have always used schemes based on the idea that Oztules links to. It may well be based on the Southern Cross as I based my original ideas on the Lucas freelite and that in turn seems to be based on the original Freelite developed in Australia.
The idea is to turn the tail at right angles to generator axis so that it turns the prop at 90deg to the wind.
With machines with slip rings this is easy to do and Elektro, Bergey and others have used it as a back up.
If you drop the cables down the centre then it becomes much more complicated as the control wire gets tangled up with the electrical ones. It can still be done with everything running down the centre with a bit of ingenuity but I have usually adopted a sliding sleeve round the outside similar to Oz's drawing. Translating the vertical sleeve movement into a direction to turn the tail through 90 deg requires a tricky bit of mechanism and I have used a lot of ways over the years, all work but none are easy to build and I seriously doubt that you could adapt the ideas to an existing furling scheme. It is a case of building it in from the start. I think this may also be true for a brake, it needs to be thought out at the start.
In dry areas where things are not going to rust up you may be able to do the brake or even a tail turner with Bowden cables but I would never have such things near anything that has to run in our climate.
Shorting is effective if the alternator is powerful enough but I like to have a back up that will stop the thing in the event of an electrical failure.
Flux