These two videos show movements. I will describe how to take the movements and use them to communicate.
To communicate you need two movements.The movement that is easier for the person to perform will be the "No" response. If it is blinking, one blink should be no. The reason for this is because a false "No" is better than a false "Yes." (Don't change mid-way. This is just confusing. Stick to what you are doing but be extra careful with "Yes"es.)
First you will teach the "No." In the above videos, the hand appears to move easier. This will be the "No." Ask obvious "No" questions. ("Is your name [obvious wrong name]?") Let the person know she can tell you "No" by moving her hand. Keep asking "Is your name [wrong name]." You want that movement strong and true.
Once you are satisfied with the "No" movement response, you can move on to yes. In the midst of your "No" questions, throw in a "Yes." ("Is your name [correct name]?" after a few wrong name questions.) Instruct her to use the foot to tell you "yes."
You now have an interactive game you can play, an "Is your name..." game. This game can be expanded into everyday life. For example, "Change the channel?" I used this in the hospital with another "vegetable". I could change the channel on her TV. (I know...we are told vegetables don't communicate. I don't think it was known how to do it.)
Don't be discouraged if "No" takes a long time. How long did it take to get the movement? Hopefully "No" won't be as long, but be prepared in case.