Scenics are the people that come in and paint the sets for photo shoots, commercials, theatre, movies, whatever.
One of the talents most sought after in a scenic, is the ability to create randomness. Though it is a skill that can be acquired to some level, there is an innate ability that some people have more than others, to understand how to make stuff look real, natural. In fact how to make plywood and plastic look so natural that you don't even notice it's there.
THAT's the real talent ... to create something that is so appropriate, it disappears.
This ability is directly related to how much you pay attention to the way stuff in nature behaves, because even though nature seems random, there is still order to it. If you know how things move (and everything does move), you can recreate it.
There's unidirectional stuff like sunlight/shadows and water leaks. Multidirectional stuff like soot, dirt, fungus, and spatter, and stuff even more random like moss, broken glass, water stains and oxidation.
Know how each behaves, moves and grows, and it will look more natural when you create it.
There's other stuff you have to know too, like the difference between how stuff looks when it is put on vs what it looks like when it is broken off.
Also, if you are 'aging' something brand new, knowing how the object might be damaged or worn through use will decide whether it really does look old, or just like an artists impression of 'old'.
Inexperienced scenics will often overdo or over-fuss a project, or else randomize in such a regular pattern that it ends up looking fake.
Random does not mean homogeneous, nor does it mean chaotic. Patterns must have movement and there must be 'silences' in the shape, to achieve the true asymmetry necessary to create 'reality'.
All this has parallels to teaching funnily enough. After all, a teacher's job is to recreate 'reality', or as close an approximation to it as possible, in a fake setting. And for that it seems you need 2 main attributes -
A grasp of what reality looks like from experience and close observation, and
The ability to create a believable approximation that another can play in.
..... And the better the teacher, the more natural their grasp of motion and the randomness that equates with nature as it really is. Not an artists impression, but as close as possible so it essentially disappears.