Regarding airbrushes, they’re great for doing large areas of fairly flat colour, like camo on aircraft, or all-over schemes, but if you’re building smaller kits then a good brush technique with quality paints thinned and given several coats works as well. A mate of mine is heavily into building armoured vehicles, mostly tanks, and he doesn’t own an airbrush, he just uses a normal brush.
The thing is, if you look at a real tank, more often than not during the war the crews painted their own tanks with whatever they could lay their hands on, and colours can be all over the place; my mate is pretty obsessive about getting it right, (he’s a goldsmith), and has often found that the colours specified by the kit manufacturers are not that accurate.
For most other people, it doesn’t matter a damn!
If you’re building a kit to place in an action diorama, then it’ll be dry-brushed with thicker paints to simulate mud and battle damage anyway.
It’s always worth visiting a museum, like Bovingdon Tank Museum, if you’re into armour, and taking photos, give a much better idea than a box illustration.