Outline the stencil on your work surface in dark red with a 0.2-mm nozzle for the edges. If you know how to draw, airbrush the shapes of the flame on the canvas. You can draw the flame any way you want it to appear.
Use a 0.4-mm needle and apply the yellow spray paint in the front center of the flame. The yellow paint should be thicker in the center of the flame; and gradually fade as you paint towards the tail of the flame. Switch the color to red and spray over the light yellow color on the tail end of the flames.
Switch to your dark blue paint. Spray the base of the flames with even strokes until completely filled. Leaving a little of the under color to show through to give the notion of real fire.
Thicken the flames with a mixture of colors to give it depth. Use a mixture of orange, yellow and dark red to thicken the flames and spray around the outline of the flames. You can use these colors one at a time or mix them together and spray them on the canvas. On the end of the flames, add touches of white to give the flames a smoke effect. Try to keep the smoke lines minimal. Remember to create the impression of a real fire.
Continue to practice until you master the art of airbrushing the look of real fire.