Brushes for writing icons

Which brushes does Peter Blackwood use for painting icons in egg tempera. Rosemary Company paint brushes: Series 22 Kolinsky round brushes - https://www.rosemaryandco.com/waterco... Series 42 Squirrel round brushes - https://www.rosemaryandco.com/waterco... Series 170 Mop brushes - https://www.rosemaryandco.com/waterco...