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Let the base layer dry.  Let the first coat dry. Then apply a second coat. You can also cut sponges to create points and edges to use for adding details.  Small, pointed brushes for painting fine details. Medium, pointed brushes for larger strokes. Large brushes for filling in larger, pre-outlined sections. Specialized brushes for more complex designs.
Consider painting the entire face or body with a light-colored base coat first. Lessens the paint's intensity and shade by thinning it with water. Make a deeper color by applying layers of paint. Choose a variety of face painting brushes depending on what design you're creating.