Stan, The Texians were indeed formally mustered into the Texas Brigade in October 1861 (they arrived in May), coincidently the time of the commissionn of Bradfute Warwick. To this date, the utltimate study is Col Harold B. Simpson's book: Hood's Texas Brigade: Lee's Grenadier Guard. I am certain you heard of it. There are highly complimentary references to the 18th Georgia. :)

http://openlibrary.org/books/OL5316529M/Hood's_Texas_Brigade_Lee's_Grenadier_Guard