Artemis BJJ (MYGYM Bristol), Can Sönmez, Bristol, UK - 03/02/2017
The orthodox version of the butterfly sweep relies on a deep underhook, then you angle out. With the shoulder clamp, which Carlos Machado refers to as the 'shoulder and chin' grip (IIRC), you can be more versatile. That's because it allows you to not only sweep with both your butterfly hooks in, but to either side as well. It also means you can sweep with both of your butterfly hooks in, rather than with one hook as you angle out to the side.
So, you have both butterfly hooks. Get your underhook as usual, but bring the other arm around their head. Lock your hands together in a gable grip (palm to palm), clamping that by their shoulder. From here, you may be able to get the sweep already, depending on their reaction. Using the elbow/upper arm of the arm behind their head, press down on the back of their head (Machado refers to this as 'swallowing' their head with your arm), simultaneously lifting with your underhook. You can then use you butterfly hook on the underhook side to flip them.
If you're not able to do that as they manage to dislodge your arm, bring the elbow underneath their head instead, into the neck. You can now lift underneath their head with your arm, while also raising your butterfly hook on the non-underhook side. That means you can flip them to the other side. A common problem in both situations is that they slip their arm out of your shoulder clamp. To tighten it up, you're going to adjust the hand that you're facing (so, the one where your knuckles are pointing at your face). From your gable grip, slide that down to your forearm and grip, while the other hand grips the other forearm. It should now be tough for your partner to free their arm.
This adjustment often happens when you've been flattened out, meaning you will need to sit back up. Also, it is hard to sweep from the forearm grip, because you lose the ability to easily press down with the elbow/upper arm or circle it under their head. Kick forward with your butterfly hooks and use that space to sit back up. You can then slide the hand back up into the gable grip and go for the sweep. Be aware that this whole process will probably tighten up the pressure on their shoulder, meaning that you need to be careful as you sweep.
Teaching Notes: Remember to keep your bum back. This sweep has the advantage that it can be done flat, but it's harder and you really need your elbow under the chin for that ideally. Again, like I said last time (if I'm reading this about to teach the butterfly sweep, remember to also check the notes on that previous post) do not drop backwards, drop sideways.