You might try a book titled "History of the Doles Cook Brigade" by Henry W. Thomas. Originally published in 1903 by the Franklin Printing and Publishing Company of Atlanta, it was reprinted by Morningside Books in 1988. The volume includes a brief history of the Fourth Georgia Infantry, and profiles of key officers. I do not know if your ancestor is listed, but it's worth taking a look! Best of luck in your search, Ron.