The difference between oil paint and acrylic paint is not insignificant, but the mediums are similar enough in behaviour and results that their application typically follows a similar procedure. Watercolour, however, is a different beast altogether. Whereas oil and acrylic are somewhat thick, opaque mediums that are typically applied to canvas, watercolour is a runny, transparent medium that is usually applied to paper. The methods for painting aircraft with oil and acrylic are similar, but the method for painting aircraft with watercolour is different.
Sketch the aircraft onto the watercolour paper. Use a hard lead pencil to make only light marks, as darker marks may show through watercolour. Use a ruler to draw any long straight edges.
Mix the colour of the aircraft on your palette. For metallic aircraft, use blue, grey and water. Test the colour on a piece of scrap paper until you have achieved the colour you desire. If the colour is too dark, add more water. If it is too light, add more paint.
Apply a light coat of paint to the aircraft.
Build up coats of paint on the body of the aircraft. Paint only one layer of paint on any reflections on the metallic part of the aircraft to make them the lightest points on the aircraft. Continue to add layers of paint to the darker areas of the aircraft until you've reached your desired depth of colour. If you are painting from a photograph, compare the painting to the photograph as you add layers of paint.
Paint the details on the aircraft using a detail brush. Represent the windows with a light blue layer of paint. Leave the lightest part of the windows white, where the glare is the brightest. Insignias and numbers are often blue, red or black. Add such details to the aircraft after the paint on the body has dried so that they do not bleed or smear.
Sketch the aircraft onto the canvas using a medium or hard lead pencil. Don't draw any minor details; simply draw the outline of the body of the plane. You may use a ruler for straight edges, but this is difficult to do on canvas.
Mix the colour of the aircraft on your palette. For a metallic aircraft, use blue, grey and white.
Apply a light coat of thinned paint to the aircraft. For acrylic paint, thin the paint with water. For oil paint, thin the paint with turpentine.
Build up thicker coats of paint on the body of the aircraft until the texture of the canvas cannot be seen through the paint. Mix white into the paint to make it lighter. Use the lighter shade to paint any reflections on the metallic part of the aircraft.
Paint the details on the aircraft using a detail brush. Paint windows with a light blue and use white where the glare on the windows is the brightest. Insignias and numbers are often blue, red or black. Use a detail brush to add the insignias and numbers to the body of the aircraft. Thin the paint with water or turpentine in order to make the paint thin enough to go on smoothly. Allow the paint on the body of the aircraft to dry before painting insignias and other details over it to prevent the paint from smearing.
Look at a photograph of an aircraft as you work in order to limit mistakes. Make sure the picture is detailed, large and in focus. Acrylic paint dries much more quickly than oil paint. To blend colours with acrylic paint, you need to act quickly, or thin the paint with water to keep it wet for a longer period.