How to Revive Old Dried Up Paintbrushes: 1 glass cup with about 1-2 inches distilled white vinegar. Heat it in the microwave for 1-1.5 minutes then put your nasty paintbrushes into it. Its supposed to bubble. It will smell horrid apparently. Let them sit for an hour where no one will be bothered by the smell. Brush paint off - she gives ideas on what to use and next steps if this doesn't work!