In the old "stickies" where I have a listing of Confederate Generals and their particulars; General Longstreet's Brigadier General's commission was issued in June, 1861.
If memory serves me correctly, after submitting it --as seen above, where he was assigned--the papers for resignation were submitted to the officer in charge of his post/assignment. Once submitted and accepted, Longstreet submitted for leave, which again--usually approved and using up his balance of leave, permitted him the travel.
Personally, I think Major James Longstreet, USA Pay Master did the most admirable and honorable submission of his resignation. By taking leave, he was now on 'personal business' to which the military could not interfere unless an emergency. The superiors knew he was going to the CSA, as most others did because of the loyalty to state over Federal Government, et.al.
Reading General Longstreet's resignation, I appreciate the man and enjoy the handwriting. It will be lost for good after his wounding in the neck where he would loose control over his writing hand. He struggled to regain use of his right hand at the same time tackling the art of handwriting with his left.
Just some personal thoughts and opinions.
M. E. Wolf