So this is not about the Arma integration, but about modeling-texturing itself, for this kind of levels. Here is a tutorial series from Radiant (Call of duty) patch modeling, it's very relevant even for modeling in other engines / other softwares https://www.youtube.com/watch?v=3EmyjrIELjg Check the youtube channel for…
Arma 3: How to make and import custom textures into Arma 3 via Editor - Bing video quick search i see at least five tutorials like this ^ I skimmed through a couple and it looks like most vehicles are using a single texture image for most of the body. Probably other parts use another, and of course there is extra decals…