An interesting choice of Impression - and a fairly easy one to document and outfit, as well.
Here's a thumbnail sketch of the Civil War and the guys who were 'In the Rear with the Gear'.
The number of citizens necessarily employed in the different Departments of an Army is immense - and the various Quartermasters, Commissaries, Provost-Marshals, Provost-Judges, and Chiefs of Police, if not themselves civilians, must have capable clerks who are.
Then - there are Wagonmasters, Agents, Teamsters, Scouts, and even Spies, all of whom come under the supervision and pay of the Quartermaster.
In one Army of the Union alone - there are about 3,000 wagons, most of which are six-mule teams.
One wagon allocated per Regiment, 10 to the Brigade, and in the Batteries - one to each gun.
In addition to these 'regular' Trains, there are also several extras.
In the Order of March, 100 wagons extend over a mile of road; and if all the wagons in this Army were formed in one line, they would extend 30 miles.
The number of ambulances is about 600.
The horses and mules number about 50,000 head.
The Quartermaster's Department of the Army employs in the neighborhood of 3,000 men as mechanics and laborers who are engaged in shoeing horses, repairing wagons, making and repairing harness, and in divers other ways.
Probably an equal number are similarly employed at other places.
As you can see - many diverse opportunities are available to enhance your Impression.
Good Luck.
Scouts Out!