Paint thinner is commonly used to remove all types of paint from paintbrushes. If using paint thinner, you will need to provide your work area with proper ventilation. If possible, use the paint thinner outdoors. If you cannot work outside, open doors and windows and use fans to circulate the air. Before the brushes can be cleaned, you will need to remove all excess oil-based paint from the brushes. Wrap a piece of newspaper around the metal section of the paintbrush and squeeze the newspaper tight while moving up the paper up and across the brush. Essentially, you are squeezing the oil-based paint from the brush's bristles. Repeat this process several times using a clean area of the newspaper.
To keep your brushes looking their best and in proper working order, clean them as soon as you are finished using them. Cleaning oil-based paint from the brushes is easiest done with paint thinner. The thinner will need to be poured into a small container, preferably with a lid so the left-over chemical can be stored away until future use. If paint thinner is not available, use turpentine instead. Place the bristle part of the paintbrush into the container. Begin to rub the brush against the bottom of the container and lightly swirl it around the in the paint thinner. Squeeze the paint thinner out of the brush with newspapers. Wrap the newspapers around the brush and squeeze in the same manner as you did to remove the excess oil-based paint.
Even after the use of paint thinner, the brushes will still be tinted the color of the oil-based paint. Typically, this tint can be removed by placing a few drops of mild dish-washing liquid into the palm of your hand and scrubbing the brush back and forth. The soap will help remove the leftover tint from the bristles. You may need to rinse the brush and your hand and repeat the process several times until all the tint is removed and the brush is restored to its natural color.
You must rinse the paint brushes completely with cool water to prevent the bristles from hardening during the dry process. Once you have completely rinsed the brushes, lay them on top of several folded newspapers. It may take several hours for the brushes to dry completely, so it is best to keep them in an out-of-the-way location where they can dry undisturbed.