At the 2016 SAG Awards, the 16-year-old actress revealed Jones, 38, told her the best way of posing on the red carpet.
"She told me, and this is a very useful tip that I've used every day since...she was saying, 'You've got to start on one end and then go all the way down 'cause everyone's kind of yelling and stuff.' To avoid looking like a crazy person, you got to really calmly like, shhhh, do that," Kiernan told E! News' Brad Goreski exclusively, offering a physical demonstration.
Kiernan, who walked the red carpet in a strapless, eggplant floral Erdem gown, had three weeks ago posted on Instagram a birthday shout-out to Jones, during which she mentioned her red carpet advice.
"Happy belated bday to the gal who taught me how to pose for a red carpet and has been a really awesome friend in my life since I was 6," she wrote. "Love you, Jan."
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Mad Men, which ended its seven-season run last year, is nominated for two SAG Awards, including Outstanding Performance by an Ensemble in a Drama Series. The show won the award in 2010.
E!'s Screen Actors Guild Awards coverage airs Saturday at 6 p.m. ET / 3 p.m. PT. Also, don't miss the Fashion Police Screen Actors Guild Awards special Monday at 8 p.m. only on E!