1. Wipe as much paint off on to a paper towel as possible!!!
2. Clean brush in thinner, (water for Acrylics, Solvent for Oils) wiping lose paint onto paper towel until brush appears clean and there is no more color coming off of the brush.
3. Optional for Oil painters: If you are using OMS (Odorless Mineral Spirits) as your Thinner i.e Gamsol, Webber Terpenoid, Mona Lisa, than I highly recommend including this step! In a separate brush cleaning tank, keep "Terpenoid Natural" (made from orange peels). Clean your bush in the same manner as in step two, following step 2. You will be amazed at how much more paint comes out of your brush that was missed by the OMS. This will save you time at the sink, and rid the brush from most of the toxic Solvent, making it safer to handle.
4. Wet the brush with warm water for oils, cool water for acrylics. If the warm water is too hot for your hands, it is too hot for your brush, it can actually melt the glue inside the ferrel. Soap up both sides of the brush, then rigorously stroke the brush against a stiff surface going IN ONE DIRECTION ONLY. Good cleaning surfaces include the inside of a halved tennis ball, the inside lid of your soap box, the basin of your sink or the inside of your hand (better after the first shampooing to get most of the nasty stuff out of the brush before it repeatedly rubs against your hand). You can be aggressive, make sure you are pressing the brush all the way down to the ferrel so that the bristles splay out. I usually use a bar of Ivory soap, though the more expensive "Master' brush cleaner and preserver" is lovely as well. DO NOT use an antibacterial soap, it will dry out your brush.
You will notice that bubbles will form on the top, not the bottom of the brush, and a "T" shape of color will appear in the middle of the brush and at the base of the ferrel. This is happening because you are successfully pushing all of the paint from one side of the brush out the other, leaving no paint on the inside.
5. Rinse. If the soap was colored before, repeat the shampooing, this time on the other side.
7. Towel dry the handle, ferrel and hair. Re-shape the hair with your finger tips.
8. Lay flat to dry over night before storing upright or in brush carrier. If you don't allow your brush to dry flat before storing up right, the excel moisture will seep into the wooden handle causing it to expand. The lacquer will then chip off, the ferrel will get wobbly or fall off and the inside of the ferrel can rust, causing the hairs to fall out.
9. If you have a flat, bright or filbert brush that has become bushy and you want to make it like new again, cut a strip of cardboard or card stock roughly 2" x 6". fold it in half, making it 2" x 3". clamp it over the brush, not letting the tip of the brush hit the fold. Secure the cardboard with large office clips or rubber bands. Allow the brush to dry laying down. When you remove the board, you will have a brush with gorgeous chiseled edges!