Did you use baby signing?

I posted this over at BlogFrog in one of the communities I am a part of, but I know I can get some great insights here, too.

I am wondering if I am doing this right. I am SO FREAKING TIRED of my 15 (nearly 16) month old pulling on my shirt when he wants to nurse, so I am attempting some baby sign language with him. We're starting with the sign for milk.

So, what I have been doing for the past several days is when he pulls on my shirt, I tell him, "Say: 'I want to nurse' " and I do the sign. Then I pick him up and begin nursing him and repeat that while doing the sign.

Well, this morning he did the sign AFTER he had begun nursing.

Am I reinforcing this wrong?