There are a lot of possible ways to fill. Have never used without some type of fill. If you decide to use would love to let me know as I am curious to see how others might use this, fill it and any variations. Here is the step out.
Here are some examples of when I have used it
This one of the first attempts at using the black tiles. Did not attempt any shading. Still not comfortable with that part of it. Will have to do more of these to get the hang of using the white charcoal pencil.This though I think had too much fill to do much shading.
Here is an example of where I had to modify it because of space. I tried putting in the small circles in the center of the feathers with a white gel pen but did not like the way it looked so just put black over them.
Interested in any attempts to use and how it has worked for you. Have fun with it.