Blue Italian Brushes - Artisan Paint Company - I Restore Stuff
Amazon.com: Escoda Global Art Materials Natural Bristle Domed Restore Premium Brush, 4/Medium : Home & Kitchen
How I restore paint brushes with stray bristles — Artoholic Studio
Watercolor Brushes: 10 Tips for Proper Care — Scratchmade Journal
Not very glamorous, but hopefully quite useful. I made a tutorial on how to revive cheap synthetic paintbrushes and fix the notorious "hooked tip". : r/minipainting