Joseph Robert Carroll has written the best, perhaps even the only, complete tutorial in conducting chant according to the Solesmes method, which is known as chironomy. This guide was first published in 1955 by the Gregorian Institute of America, and is republished in 2009 by the Church Music Association of America. It is no substitute for a live lesson but it is the best tutorial in print.
Here it is in print.
Here it is in free download.