This is an in depth look at how I do the Kimura from Closed Guard and a look at how to overcome the most basic defense for the Kimura.
As you notice I start off by dominating the arm and not by clasping the wrist. This is different than I was originally taught. I made this change after many hours of application after I realized that controlling the wrist not only alerts your opponent to your intentions but also leads to a lower percentage finish.
Once you get your Kimura grip on the arm the goal is to make your body rigid (on the side that you are finishing the Kimura) and move your butt to the outside of your opponents leg. By doing this you are making sure to eliminate any chances of your opponent maintaining a grip on the inside of their pants. In the event they do get their hand to the inside of their thigh then it will be all the core muscles against their hand and arm muscles. Almost all of the time this will ensure that you get the finish.
Notice that after I break the grip away from the thigh I take my leg to the outside of their arm. Not only does this help me move their hand to their spine it makes sure that my opponent has nothing else to grab onto.
Make sure their hand is as close to their spine as possible as this will greatly increase the pressure generated and remove all the slack from the joint. Make sure to go slowly as the pressure will come on much faster.