Don't be daunted, it just takes time. You'll get faster at it with practice, but the first step is simply brute force, or at least it was for me. Take a picture of something simple, recreate it in 3D with exacting detail. When something doesn't match you drill down, find the optical phenomenon that you weren't modeling correctly, and fix it.

That's it. There's no shortcut to being good at this stuff, you just have to learn how the real world works and make sure that when you're simulating it in the computer you're using physically correct numbers for everything. Relentlessly comparing what you're doing to photographs is the only way to truly master the skill. It's a lot easier to take a step back and do stylized realism once you can nail the real thing.

That being said this is fantastically executed. I'm especially loving the ability to mix the baked GI live, it's a great effect for static scenes like this.

P.S. Ok I probably lied when I said there are no shortcuts. Here are a few:

- use a physically based (preferably unbiased) renderer

- use only energy conserving materials

- use light-probes to light your scene