...why not have the part timers do everything instead of pre-painting it for them? And wouldn't an airbrush or spray cans be more efficient than handbrushing?

djseifer said:

...why not have the part timers do everything instead of pre-painting it for them? And wouldn't an airbrush or spray cans be more efficient than handbrushing?

Gensoukyou, common sense.

Yeah, it's canon common sense.

From Symposium of Post-mysticism (underlined by me)

When the end of autumn approaches, her power causes the trees to turn a fiery red: the so-called autumn colors. Since she has to thoroughly paint each leaf one by one, she can't prevent some unevenness from appearing. That's why yellow and dark brown are also mixed in.