First of all, forgive the sloppiness of the first armbar. When you look like a giant pillow, it’s hard to make it look pretty. That said, here’s the Judo armbar from Big Guy BJJ.
What makes it Judo styled is that it’s quick, and rolls the opponent before locking in the submission (very similar to how Ronda Rousey has finished a few armbars).
It’s important to remember that if your opponent won’t roll over of you, but tries to stay in their turtle, you can always grab the pants and pull their leg towards your head to make them roll anyways.
Often, big guys try and avoid working a bottom game because it’s harder for them to move around on bottom than it is on top. This is a great way to submit an opponent from the bottom position. Let us know what you think!