Being able to paint can be really handy for lighting. When I begin lighting a scene, I like to have a really clear idea of the image I'm after. A paint-over only takes 10-20 minutes to make, so if I don't have a lighting key from vis-dev, I will make my own by painting over a rough render. Sometimes I show these to my supervisor to get their feedback before I start lighting and it saves a lot of time because they can tell me whether I'm going in the right direction before I even start.
This still-life in Zootopia+ was a one-off shot with no key shot to match, so the lighting was up to me. This was how the rough render looked before I started lighting:
And here was the paintover I made. I wanted to emphasize the candle light as the main light source, and give a warm glow to table because it is a shrine to Grandmama, the cannoli baker. I painted directly over the render in Procreate.
When I did the lighting, I took all of my ideas from the paint-over a step further and made the candlelight even warmer and softer.
Here is one more from Raya and the Last Dragon. The raw render:
And the final lighting: