Trace the outline of the design using the outliner and wait a couple of hours to dry.
Using the different coloured paints fill in the outlined shapes. The paint is very thick and opaque when wet, which makes it hard to see any air bubbles which might be present.
Using a pin move the surface of the paint to bring any air bubbles to the surface, which can then be popped by the pin.
Allow the paint to dry overnight, it will then turn transparent when dry, unless it is meant to be opaque.