You can make any type of plastic that can be painted look like wood, for stage plays, movies and other applications. Many car interiors use plastic painted to match the grain of wood, instead of real wood. Making plastic look like wood takes just a little bit of painting skill, the right brushes and the right types of paint.
Assess your type of plastic. How well will the paint stick? If it is a slick surface, you might want to rough it up with a very high-grain sandpaper, 120 grit or higher. Just sand very lightly until the sheer surface is off. Creating a few grooves with the sandpaper will also give your plastic the feel and rough look of wood.
Paint on one layer of primer in either grey, yellow or cream. This colour will show through the next layer of paint, so match it to the type of wood you are trying to imitate.
Mix your umber or brown colour paint with white until you get the colour you are seeking. This will be the second layer and should look like the wood's flesh colour, the colour without stain.
Brush on the wood colour paint using quick strokes.
Mix a slightly darker version of this same colour by adding black or more umber or brown. Then brush this into the wet paint using quick strokes and a thin brush to create those grainy patterns you always see in wood. Go ahead and darken the paint even more, and draw a few thinner lines and knots. Make big blobs with the brush, then brush out any unwanted strokes with the lighter colour.
Mix up a stain in a natural wood colour. Brush this over the plastic after the paint has fully dried. You now have a piece of plastic that looks like wood.
Mixing paint to the right colour is the most important step. If you look closely at wood, it is not a real dark brown, but a tan, pale colour, closer to white. The brown or umber colour you mix into the paint should not overpower the white. To get a real pine colour, use yellow, then a simple, very light tan colour, with a natural stain. You can also use a very fat brush, lightly dipped into the dark brown grain colour to create the wood grain. Lightly swath this over the plastic, barely touching the wood. It's more difficult to do but can create great effects.
Don't make your paint too brown, or your plastic will not look as realistic.