Does anyone know about using a keyboard during a video call...?
I think if I can write what I want to tell him and he reads like close-caption does during a movie...?
If you are using Skype you can use the messaging system bar at the bottom of the display screen. You cannot use the Skype message line and keyboard in full screen mode. Skype is free.
I have used
PalTalk in the past to do what you're looking for. I'm not sure if their free version still has that feature though, haven't used it in a number of years now.
Sign to him?
How do you talk to him in person, its a video call, just do the same.
Depends on what OS and Video software you are running
NetMeeting used to do that under Windows XP. Of course if he can see you, a legal pad and pen are always a good standby ... I'm not certain what the Windows Live! online offerings are, but if you are running Vista on up you might sign up and check out their services.
I believe you can do this in Google Hangouts! Upgrade to Google+ and you can start a "hangout" which uses video and chatting.