Another recommendation that has been wonderfully helpful are the signing time series of videos.
Signing Time

Our nephew used baby sign language and it made his ability to communicate and our ability to understand him a whole lot easier.

The videos have catchy songs that sit in your head all day, but also sit in our little Colton’s head too. He has been able to communicate basic words before he could talk and even now, when we have trouble understanding him he is able to sign.

Sharpteam recommends baby signing time:

Cole's Words