How can fiction writing be best used for achieving enlightenment? It seems that many fiction writers were very wise, including those, who had little or no access to spiritual teachings (e. g. the Strugatsky brothers).

Allegedly, in Japanese culture non-spiritual activities (tea ceremony, archery, calligraphy, martial arts) are being used as tools for spiritual development. I heard some people say that any activity can be used for approaching enlightenment.

If it's true, then fiction writing can be used in the same way as well. 

If someone spends a lot of time and energy writing fiction books (they regard it as the most important part of life), what can they do in order to get maximum spiritual benefit from this activity?

I. e. if the enlightenment is the goal, and fiction writing is the engine, what kind of maintenance acts is necessary to reach the goal using that engine?

Notes:


Preferably, it should be concrete advice, ideally with some data supporting it.
Those recommendations should be compatible with (or adaptable to) the Diamond Way Buddhism.
I may not know much about Buddhism, but as I understand it mindfulness is probably the best way to achieve enlightenment. 

Essentially, enlightenment is understanding everything, having all the walls torn down in your mind and being open to the oneness of the universe. Thus, in order to understand everything, you have to begin to understand something. You may be in luck, because it looks like you've already found the thing you want to understand. 

So, in terms of fiction writing, it's a very artistic pursuit, and something I and many other artists understand is that our work is never complete, never perfect. There's always a way to improve, no matter how good we get. This process of improving one's skills, honing one's talents, reaching ever closer to perfection, is very close to the process of achieving enlightenment. The only difference is that it is very limited in its scope, but I believe even this is only a temporary hurdle. 

In my own pursuit of fiction-writing perfection, I've discovered many great and interesting things. In order to make my worlds feel real, I've had to better understand our own world (I'd really recommend looking at Worldbuilding SE). To write better characters, I have to understand the human condition. In general, I've realized that in order to be a perfect writer, I would have to achieve enlightenment; otherwise, anything I write would be lacking in some aspect due to my own inadequacy. 

For the most part, I believe this process is natural; people who like doing a thing naturally want to get better at it, and getting better at pretty much anything will naturally lead to getting better at other things. But I would also say that being aware of this process from the start is much easier than figuring it out on your own. 

So my suggestion to you is to just be aware of your art, and what it is, and how it is linked to everything else. Never stop trying to improve, and never limit yourself; always be open to new concepts, new ideas, and new ways to get better.