Here is a cool technique for working your triangle defense. We call this move the wedge. It can be used as a stalemate or as a way to pop open your opponent's figure four'd legs.
When working this techniqe, try not to let your opponent pass your arm or underhook to leg.
Here is a video of Lockflow member "Bawajiwe" and I working it, and the step by step is below.
Here, Eddie has me trapped in a triangle.
I quickly lock my hands together, making a frame against Eddie's stomach as I arch my head up. This buys me a few moments of breathing time and makes it harder for Eddie to pass my arm across.
Close up of step 2
Here is a close up of the hand position
I drop my trapped arm's elbow to the mat as I keep my grip and frame tight
Close up of step 3
Here is a close up of the elbow dropping to the mat
As soon as my elbow touches the mat, I drop my hand down so that my forearm is flat with the mat, I reach my palm into Eddie's ribs and push against them to help drive my elbow back. This motion should make it very difficult for your opponent to tighten the triangle any farther.
Close up of step 4
Here is a close up of the hand and arm positioning.
Using your legs to walk towards your opponent's back and pressure of the wedge, you may also be able to pop your opponent's legs apart from the fig 4 grip.