Combing the paint on the surface with the combing tool (or toothpicks) is done to remove air bubbles in the paint, and to blend colors together. The arrows shown on the design indicate the final direction in which to ‘move’ the paint once you've blended it together.
Use the pointed end of the combing tool (you can also use toothpicks) to ‘move’ the paint to blend it, first north and south, then east and west, and lastly again in the direction of the arrows shown on the pattern for the combing in each section. (Don't be tempted to ignore the arrows; the final direction of the paint does influence the end result.)
As you paint, comb, and blend a section, regularly tap the underside of the surface directly under the section you are working on to help reduce air bubbles in the paint. (The handle of a combing tool works well for this.) You may find it easier to work over a light table so you can readily see the bubbles. You should always comb and tap sections as you paint, whether you’re blending colors or not.
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