All the locking skills should be trained in pairs and in reverse order.
- You straighten your opponent's arm, your opponent resists (he doesn't want his arm to be straight), you borrow his resistance force, bend his arm, and lock his elbow joint.
- You bend your opponent's arm, your opponent resists (he doesn't want his arm to be bent), you borrow his resistance force, straight his arm, and lock his shoulder joint.
Aikido follows this principle very well.
It's interested that we can't find many Aikido videos that show "how to counter a particular joint lock". Does anybody know why?