Primer is used to pre-treat surfaces prior to painting them. Primer is also used to prepare surfaces such as plastic or metal, which do not allow standard paints to attach to them very well. Making your own primer is a cost-saving method that can be done when painting a wood or drywall surface, such as the walls of your house. The paint you will be using as a top coat is easily thinned to function as a smoothing agent on the surface.
Purchase standard paint that can be diluted with water or mineral oil. Purchase mineral oil if that is how the paint needs to be thinned. You will need about half the number of gallons of paint and mineral oil that it would take to paint the entire surface.
Open the can, and stir the paint in a circular motion for about 1 minute -- or until the color is uniformly distributed.
Pour about half of the can of paint into the empty paint can.
Fill the remainder of the paint can with either water or mineral oil, depending on what the manufacturer says is the best way to dilute it. There should be a 1-1 ratio of paint to diluting substance.
Place the lid on the paint can, and hammer it securely into place. Shake the paint can vigorously for approximately 30 seconds. Remove the lid, and then stir the primer until the two solutions appear to be evenly mixed. Apply the primer to the surface immediately, and allow it to dry thoroughly before painting over it.