I always try to do a few things to prevent from even getting there:
- big chest.. a lot of people bring their shoulders in and become small while they try to hide their head to block the foot from coming in from of the face. You opponent needs to bring his thigh up before he even swivels his shin. If you make a big chest and flex your lats, you can sort of keep his thigh pushed back
- head position.. while some people are super flexible, it's easier for your opponent to slightly angle their body in an oma plata type direction. I like to drive my head under their chin in a way that prevents them from moving their head to that side
- control their hip.. just as many opponents like to move their head in oma plata direction, their hips swivel a little in the opposite direction. I like to post on my foot and drive my knee into that side of their hip, to keep their hips directly in front of me.
This points aren't so much of an escape as they are general prevention details as your opponent is working the over arm wrap and grabbing their shin or foot