T.B.
I always say:
"Give so and so a hug and tell them bye bye!"
or
"Tell Grandma Thank you for dinner and give her a hug bye bye."
He usually does it, if not I just model it (do it myself and with the baby) for him and let it go! It's worse to keep nagging and have him yelling and crying that he doesn't want to! Embarrasing!!