When you have allowed your paint brushes to harden with paint on them, you can easily soften them by placing them in hot vinegar until paint loosens and the wash them in hot soapy water.
The best course of action for maintaining your paint brushes is to clean them thoroughly after every use. But there are times when this does not happen. Depending on the type of paint used there are ways to revive a stiff brush and remove the old paint. You can even temporarily slow or stop the loss of bristles. This page contains several suggestions for repairing paint brushes.
