Revive Old Paintbrushes...Soak gunked-up nylon brushes in hot vinegar for up to 30 minutes to remove paint and soften the bristles. Afterward, wash them in hot, soapy water, brushing off paint as needed, then rinse and let drygood as new.
How to restore an old good brush? I found out that by not only adding soap but really hot water the oil sticked to the brushes it will finally come off! Leave the brushes in hot water for couple of minutes until the brush hairs are flexible. Now, I have brushes in great condition that I have used for more than 10 years just like new! The best of all I didn't use turpentine or thinner at all that it is toxic.