This is the second page of the coloring book for my first partner. This page was filled in with Tombow dual tip markers. I used a subtractive method on this page. First, the page is filled in with markers. This method works well because Tombow markers are very heavily pigmented. The page is then lightly misted with water. The final step is to take a paper towel and place on top of the wet surface. Press down (do not wipe since you don't want the ink to spread). Lift the paper towel and continue to blot the page (do not re-mist) until you reach the level of coverage you desire.
This technique mutes the colors a little, especially if you use bold colors like I did.
The above image is the blotted paper towel. I am sure that if I used an absorbent artist's paper that I could have used this blotting image as a basis of some other artwork.