It's a work in progress. My main concern in the 2 ish hours I put in so far is purely tonal. Those are going to be backed up by something bigger later (Taiko style drums probably), but initially they are there to 1, Give a military feel and 2. introduce the chugging guitar rhythm
Kinda like drawing Blocking out main stuff and implying tone happens first. Details and shading happen progressively and usually after blocking.
That's my process anyway