I'm keen to try this too. I ordered a baby signs chart from the internet as my bub spontaneously started using an arm signal for "milk" from about 8 weeks - tho i'm still not sure if i am imagining it, but it's consistent when I put him in the position for breastfeeding, or if i stop feeding him before he's finished. It's a straight arm brought down quickly from head to hip. He doesn't have the hand skills for any other signs tho (and his "milk" sign isn't the one that's used on the chart - he uses a particular whole arm movement) - but i'll probably start using some basic ones to get him used to it.

The chart was about $17, you should be able to google "baby sign chart" or "baby signlanguage chart".