First you need to have your brushes dry to avoid diluting the liquid soap.
1) Pour some Brushflush in a container such as yogurt, glass jar or anything similar
2) Take a few brushes , 2 or 3 of similar size, and vigorously stir them in the soap, making sure that the liquid soap in inside the hair, particularly at the base of the brush near the metal ferrule.
3) When your brushes are soaking in the soap, lay them flat either on a plastic bag, a tray, slightly inclined towards the hair to let the soap flow towards the hair, away from the handle.
4) Let them sit there at from 2 to 5 days. You can turn them, making sure that the soap penetrates deeply in the hair. Brushflush will continue to breakdown oil molecules even when it is dry.
5) Put on your plastic gloves when you are ready to wash your brushes and rinse your brushes under lukewarm water. Do not be afraid to damage the hair. Rub the brushes into the palm of your hand and clean them until the suds are perfectly clean. This will take several rinses. Gently squeeze the suds from the ferrule to the tip (just like blowing a child’s nose). Repeat this cycle until the suds are white with no color and of very small bubbles. I always wash them with liquid dish soap at this stage. Rinse thoroughly.
6) When your brushes are clean, and totally free of soap, no suds coming out when you squeeze the bristles, take a cotton rag and dry them, reshaping them.
7) Lay them flat - horizontal. Outdoors under sunlight is perfect. Never , ever, leave your brushes standing on the tip of their bristles. It is impossible to reshape them. Do not dry your brushes vertical, the humidity will get in the handle and the ferrule will become loose and will turn.
8) You have to wait that your brushes are totally dry before you can use them again. It takes about 24 hours, depending on the heat and humidity in the atmosphere. Do not dry them too close to a heat source. When the brushes are wet, you cannot use them for oil painting, they are too floppy to pick up paint and apply it. So it means that you have to wash your brushes at least 24 hours before you want to use them. There is no problem what so ever to keep your brushes in the soap for weeks. That is what I do because I do not want to wash brushes every week. That is presuming that you have enough brushes to get around.
9) If you have oil paint on your clothes and want to get rid of it, use Brushflush directly on the fabric, make it penetrate really well, and let it sit at least for a few hours, a day is better. Then just wash with your laundry. We call it “miracle soap.”
Never use paint thinner to clean paint on your clothes, it will push the oil into the fabric and accelerate the drying.
10) You can do this every 3 weeks or so, or when you see the hair of your brush is not soft and flexible anymore.