You got to be prepared to defend the neck at all times by framing until you are in the right spot to get to dogfight or for Old school, but then again going back and forth ( dip setting) is always necessary always remembering not to ever let them get their left arm around your neck at all times, especially against gangster guillotine fighters in the dojo. I have spent ages on just good habits in halfguard ( Thankyou Brent Little). A combination of all the suggestions is great I think. Boa has to be really low and the use of your left arm to swim in to mechanic and back again to old school or dogfight is key for me surviving the attack inside my own half guard. You cannot break concentration ever inside that position. As a guillotine enthusiast, I know what I am looking for to take the choke into effect. Then I just reverse engineer it to work on the defences to it too. Works most of the time but you can still get caught...thats what makes it jiu jitsu!