I've been experimenting with different art materials lately and came across Pan Pastels, which are loaded with lots of pigment and are fun to use. They come in small discs of color, each called a pan. You simply rub the pan in a circular motion with a Softt (Tm) Art sponge (I use sponges bought in the cosmetics department of my local store, which work just fine). It's sort of like applying make-up; you load up your sponge and drag it across your surface (in this case, stretched canvas). You can block in large areas of color, build layers, and work in fine details. They are compatible with conventional pastel fixatives, and can even be erased from the paper using any artist's eraser.
For She-Fish I used collage, Pan pastels, markers and acrylic. When my boys were little, I used to decorate their bedroom with photos and art that would last over many years and still be age appropriate (animals, nature, sports). I think this would be perfect for a child's bedroom, adding color and whimsy!
Check out Pan Pastels on YouTube for more detailed instruction on their use, and have fun creating.