Two of my books will be helpful to you. There is a brief summary of the 18th Louisiana Infantry Regiment and 18th Consolidated Infantry Regiment in "Guide to Louisiana Confederate Military Units, 1861-1865" (LSU Press, 1989). "The Civil War Reminiscences of Major Silas T. Grisamore, CSA" (LSU Press, 1993) is the memoir of a man who served initially as a sergeant in Company G, 18th Louisiana Infantry, and eventually became a quartermaster officer. He was with or near the regiment until the end of the war.