There are a couple of things going on here that have to be done carefully so you don’t hurt your partner.
However, done at full speed, it all happens very quickly.
Arm Crank
This technique can be done with or without the Arm Crank, but the Arm Crank adds just one more element to this counter.
Even if you don’t quite get the crank, your opponent will naturally react by retracting his arm, which pulls you right into the choke.
This is a great demonstration of using one technique to set you up for another.
Head & Arm Choke
The choke itself should be secured before you take the guy down.
You’ll be using his own shoulder to cut off the blood on one side of the neck, so press your head in tight.
Once it’s tight, take him down by stepping–almost kicking–behind his leg.
Don’t just step behind and try to trip him.
As he goes down, pay attention to your own position.
Otherwise, you’ll just fall down with him.
Keep your weight a little back to keep your balance and press all of your weight into him using your back foot.