In S05E02 of The Americans, Phillip and Elizabeth teach their daughter, Paige, a technique to use if she is in distress and it feels like she's about to disclose her parents' real identity to her boyfriend:
Rub her forefinger and thumb together and think about her parents.
Have either of the Jennings parents used this technique themselves in previous episodes?
No, they've not used that technique. But then again, Phillip and Elizabeth are experienced and well-trained spies. I would think their need to use such a crutch disappeared long ago. I would also think that to lie convincingly, keeping calm, and manage stress would've been addressed during their training.
Anyway it looks like a post-hypnotic trigger - probably some sort of auto-hypnosis - so they may use another (more discrete) trigger... and after using it enough times, you really don't need the trigger - it's enough to just imagine using it (in your mind)... or with enough practice, even just willing the result (eg. to stay calm).
