I was an extra in North and South Part 2 more than 40 years ago.
Camped 3 weeks on a working cattle ranch. (Longhorn cattle are mean tempered, BTW.)
We were paid $50/day which was more than I made working at the time LOL. And they fed us breakfast and lunch every day.
Would have gotten $100 if were were members of the Extras Union but we didn't know that at the time.
One of our group played a reverend. Because he was shown giving last rites in a two-person closeup, he got residuals for years.
I was not prepared for how many takes it gets to get a scene just right.
It's hard work actually. But it is very interesting to see how the process works. And I got in a few scenes that made it on screen. Mostly the Antietam scenes.
BTW if you do this, try to avoid the buried charges that simulate shell explosions. The "dirt" they throw out is actually fresh sheep manure. And yes it smells bad!