The 'long' hose that is routed around the neck is 'long'. Not the same as a 36~40" octopus hose. It should be 5' minimum for you to be able to route it that way.
Then you route the hose under your right arm, across your chest, and then around your neck over your left shoulder, and finally coming around from the behind from the right. If you have the correct length hose, there is no way you can get entangled or get choked. Divers in overhead environments use a 7' hose in order to be able to swim single file while air sharing. With this hose, the difference is you tuck the excess hose under your harness or more preferably route it under a canister light or knife on your harness waist belt. The optimal length may vary slightly depending on the diver's height and size.
If you are just using a standard octopus hose, then just use it as you would a normal hose. It will be a little loopy, though. The short hose second stage(your backup) will be attached to a bungee necklace and hung from your neck. (DIR gear advice also makes this as short as possible without restricting movement. 22~24" as opposed to the usual 32" hose.)
BTW, once you try sharing air with a 'long' hose and then try sharing air with an 'octopus' hose, you will really appreciate the value of the long hose.