I searched for instruction on making a wheat chain about 3 years ago and found nothing so I would love to have you post results if you find something. I went to many of the links Google found and none were instructions, mostly chat about various definitions of wheat and rope (sorry rc. but the article titles are very misleading. For example, the YouTube instruction video was actually about buying the chain on one of those TV shopping channels).
I have 2 versions (variations?) of the Jean Stark book and found neither satisfactory on the subject of wheat. However it is a good book for chainmaking in general. But an expensive misdirection if you only want instruction on wheat chain.