Billy,

Now let me try and answer some of your specific questions by using multiple posts to keep them shorter and readable. Some of your questions over lap into others, so pardon my redundancy in those cases.

So would it be safe to presume that in, for example, May of 1862 Frost's artillery brigade consisted of Hoxton's, Landis's and Guibor's batteries?

I’m going to leave the speculations to you and others, but I can the following additional facts:

6/28 G O #2 Priceville-Maury cdg-Arty park of Army of West to break up & Btrys to their Bgdes
I the Arty Park of this army will be broken up at once. The Btrys of Bledsoe, Lucas & Macdonald will report to their respective Bgde Cdrs.
Capt Hoxton Cdg the reserve Arty will act as chief of Arty during the temporary absence of that officer. He will select a new position for its encampment where better water, shade & Grass can be procured & where there is proper ground for drilling at the maneuvers of Field Arty.
II …The staff section of Arty under command of Capt Brown will at once be consolidated with the incomplete Btry of Capt Guibor. Capt Brown is hereby appointed 1st Lt of Capt Guibor's Btry The two Lt’s serving with Capt Brown's 1/2 section & the junior Lt of Guibor's Btry are supernumerary officers & will be reported accordingly Each Btry Cdr whether attached to a Bgde or not will render the weekly reports to the office of the Chief of Arty required by him.
III the Bgde Cdrs in person and through the Bgde Inspectors will ensure attention to the strict enforcement of these orders in the Btrys of their respective commands.
By comd of Gen Maury Cdg Army of the West Official D W Floweree AAG James M Loughborough A.A.G

6/30 A of the West Reserve Btrys: Captains Hoxton's, Landis', Guibor's, & Brown's

6/30 S O #3
-Guibor Btry from Army of West to chief of Arty of dept
-The half section of arty Capt Brown cdg will at once be consol w/the-incomplete Btry of Capt Guibor-Brown is apptd 1st Lt of Guibor Btry
By order of Gen Maury-cdg Army of the West

--------9/9 Maclean [Price’s AAG] writes-Capt Brown w/one sctn of Arty was ordered to report by Col Gill, chief of Arty, to Col Clark’s command of Arty Army of the West. Then understood to be the remnant of a regularly organized Arty Co which had escaped from New Orleans
Capt Guibor commanded an Arty Co which I understood had declined to elect any officers refusing whatever any election. That officers were appointed and as some of the Co belonged to the MSG
It was not until the MSG left this army at Priceville that Capt Guibor’s Co was attached to the Arty brigade then commanded by Lt Col Major.
Shortly after Gen Maury assumed command of the A of the W and by Gen Order #2 of 6/28 consolidated the sctn under Capt Brown and the incomplete Co of Capt Guibor.

7/1 HQs A of the W, Priceville, D H Floweree to Capt L Hoxton cdg Arty Bgde-Continue the operation of the bakery until the army moves

7/6 Capt Wade’s Btry has not reported to Arty Bgde as ordered-Gen Little is asked for explanation why not

7/11 Priceville, HQs A of the W, Snead to Capt Wm Wade cdg Btry-Gen Price tenders you the appt of chief of arty of this army. It is important that this position be immediately filled. Please advise your decision

7/12 Capt Wade declines appt as chief of Arty

7/21/62 Reference to Capt Guibor cdg Arty reserve.

7/25 HQs A of the W, S O #26-The Arty Bgde is hereby disbanded and the Btrys assigned as follows:
Hoxton to Maury
Landis to Little
Guibor to Little