This is a good option for when the person sits and clears the armpit (as seen in the video. If they use the crossface it’s possible to do this as well but you should rep it out like this so you can feel the body weight transfer and learn the correct pathways.
Make sure that you enter that hand all the way under the body until you can grasp around the outside of the thigh. This will be important in both making space and having your hands in a safe position when you make it to deep half.
You’re going to need to use your legs a lot. It’s hard for me to show you really how much leg movement there is in this video without making it a 20 minute video. There is a lot going on with the pulling of your knees to your chest and then stretching them away. This will definitely take some practice before you try to bust it out while rolling