Generally speaking, you should start at the top of a piece of work and paint down. Each fresh brush stroke should overlap the one above it and mop up any surplus paint of the former brush strokes.
Paint the intricate parts first and then the plain surfaces. For instance, when painting the aeroplane weathervane, use a small brush and paint the struts first, then paint around the bases and tops of the struts on the surface of the planes. Change the small brush for a larger one and flow more paint over the surface of the planes, gathering up the paint around the ends of the struts as you paint along.
When painting a large model, such as an army truck, and not being quite sure of the quantity of paint needed, mix up enough paint to paint all the parts of the model that show the most and leave such parts as the bottom of the frame and the inside of the body until last. If you have to mix up more paint for these last parts it will not matter if it is not exactly the same shade.
If you have not had very much experience in mixing and combining colors, it is generally better to use the different tints just as they come from the cans, without trying to mix them.
Do not use too many colors on one toy, but try to get a pleasing effect with two or three colors that look well together. For instance, a truck may be painted an olive green or khaki color over its entire surface, excepting the front of the radiator which should be painted with silver paint.
When the first coat of paint is thoroughly dry, lines of black may be painted about the body and various edges emphasized with black. The hubs of the wheels, the lamps, the rim of the steering wheel, and the filler cap on the radiator may all be painted black with good effect. The part of the wheels which is supposed to represent the tires should be painted a dark gray. (Gray may be made by mixing black and white together.)
Study the large trucks seen about the streets for inspiration. These large trucks are nearly always very simply and attractively painted.
Real locomotives are painted black at present, but a small toy locomotive looks much better if the wheels are painted red (vermilion). A red band may be painted about the top of the smokestack and the tin strips framing the cab windows should be painted red, as may the number of the engine, etc.
The whistle should be painted with gold paint and also the inside of the headlight, and broad lines may be painted about the boiler with gold to represent the straps seen about locomotive boilers.
Paint the tires of the engine wheels with silver paint. The driving rods may be painted either black or silver.