I have your Joshua David Coffee listed in my book on two pages: page vIIp144 shows him as a 22-year old private in Crocker's Militia of Fannin County in July 1861 Fannin County; and page vIIp335 shows him as a deserter from Hardeman's Regt. but reenlisted on November 6, 1863 in the Confederate Brush Battalion, which was commanded by J.R. Diamond.
As far as I know, your J.D. Coffee was never in Bourland's command. But it is true that J.R. Diamond took over Bourland's Ranging Border Company on February 10, 1865, but it was a different unit than the Confederate Brush Battalion. Granted, the records are scant and I have evidences that many men did not get into the National Archival records for Bourland's Regt, but were nevertheless in Bourland's Regt.
The point I was trying to convey was that one of the best sources for the Brush Battalion is the BOURLAND PAPERS,that I have transcribed, interpreted, and indexed. Again, my web site describes my 998-page book: BOURLAND IN NORTH TEXAS AND INDIAN TERRITORY DURING THE CIVIL WAR: FORT COBB, FORT ARBUCKLE & THE WICHITA MOUNTAINS.