To make your own shimmer paints, you will need the following: a paintbrush, watercolor paints, water, and Iridescent Medium.
If you add a little Iridescent Medium with a little watercolor paint, then you will have shimmer paint. The first step is to open your watercolors. Add a little water to the colors that you want to use. Shake the Iridescent Medium, before you open it. Then, dip your paintbrush into the Iridescent Medium. Then, dip your paintbrush into the color that you want to use. Just continue in this fashion, until you are done. Allow it to dry thoroughly. You should be able to find Iridescent Medium at hobby and craft stores.