Shoe Cleaning Brush Set with Nylon, Boar and Horsehair Bristles, Wooden Sneaker Cleaner Brush for Leather, Suede, Canvas, Textile, Bags and Accessories - 3 Pack

Its safe to use a designed brush for cleaning thru hole PCBs. Brushes supplied to us were wooden handled, these work well https://www.amazon.com/Cleaner-Horsehair-Bristles-Cleaning-Accessories/dp/B0B2MGFD9T