By the time our daughter was 12 months old she had masterd 4-5 different signs. We used a regular ASL book. I'm somewhat reluctant to agree with this approach to teaching infants sign. This is one more way of contributing to the pressure to perform. Babies have a sign language of their own as it is.
Attentive parents learn to read that language.
I guess I can see good points and bad points to this issue. Anyway, I appreciate your review. The signs that are recommended for infants are very easy to make. Not much different than clapping. All of these signs are spontaneously used by infants.