I do it before, during and after. I talk to her the whole time, and then afterI do the sign I hold her hand and she her how to do it to herself. She knows when I do milk (she'll even look down at my boob and laugh!) and I think she's been doing it finally, ald tthough she seems to open and close her hand a lot so she might be playing. Hard to tell on that one!
i do potty and milk before during and after. he is doing milk now, its so cute. i still have to ask him do you want milk, then he will do it back to me if he does. he doesnt just think to do the sign without a prompt from me first. it is sooo cute. he does openoing and closing his hand on my boob a LOT while he is eating too. for signs that are labels for something i do the sign while he is looking at the thing, fish, potty, kitty, and daddy he recognizes these b/c when i do the signs he looks for them,
We just started signing about a month ago, but Aidric has already started doing toy (go figure), and he knows milk (he'll pull on my shirt), cereal and food (he opens his mouth and makes the bird-y sounds, and mommy. It's so cute!