Medium density fiberboard (MDF) is an inexpensive alternative to solid wood. When creating wooden signs, it might be advantageous to choose MDF, simply to save money and create a sturdy surface. MDF not only takes paint very well, but the surface is also smooth and free of the knots and imperfections that solid wood can have. There are many different types of MDF, but for this project it is imperative that a water-resistant board is purchased, especially if the sign is for outdoor use.
Sand the edges of the MDF until smooth. Wear a face mask and goggles to protect your eyes and lungs from the dust. Wipe away any leftover dust using a tack cloth.
Pour an oil-based enamel wood primer into the paint tray. Oil-based primers and paints are ideal for MDF outdoor signs, since this will protect the board from moisture. Make sure to use a compatible, oil-based topcoat if you are using an oil-based primer.
Apply the primer all over the board, including around the edges for maximum moisture protection. Let dry, then apply another coat. Let dry overnight.
Lightly sand the surface of the primed MDF using a fine-grade sanding sponge until the surface is smooth.
Apply a layer of oil-based enamel paint in the colour of your choice over the sign, making sure to cover the edges as well. Let dry and apply as many coats as necessary. If the paint is too thick and difficult to spread, try adding a small amount of paint thinner.
Stencil lettering, graphics or designs onto the sign using another colour of oil-based paint. Use the ruler to ensure that any text remains straight. Hand-lettering is also an option.