First - HOW TO FILL IN HOLES:
Cover the open areas with the Brush tool making sure to not go beyond the stamped image.
Painting an outline stamp is essentially the same. You just need to work with a few more layers building the colors one upon another.
HOW TO PAINT OUTLINE STAMPS:
Start with an outline stamp.
Think about what would be the very back layer of color. (In this case I wanted the inside of the design to be white.) Add a Brush Layer. Change the color and paint over the stamped image stopping at the black outline.
Send this layer behind the stamp. Add second Brush Layer. Determine what would be the next level of color. (For this card I painted over the flowers in blue and the stems in green.)
Send this layer behind the stamp. Continue adding brush layers of additional colors. (I added a third layer of lighter blue to highlight the center of flowers and a fourth with tiny dots of pink for the stamens.)
Arrange the layers with the outline stamp at the front and your image will be beautifully painted!
I will have one more tutorial tomorrow showing how to "emboss" with digital stamps!