Artist's Faux Finishing Paint Brush Lot Softening Pouncing Brushes for Stencils | eBay
Ace Hardware - Paint tip: To soften a paint brush, bring a cup of white vinegar to a boil, remove it from the heat and rest the paint-hardened bristles in it overnight.
Handover : Softening Brush Synthetic Hair 3 in | Jackson's Art Supplies