How to mark typos in brush strokes?

How to mark typos in brush calligraphy: you can circle typos; You can also explain it after signing.

This can refer to the best running script works of Wang Xizhi and Yan Zhenqing in the world, as shown in the figure:

Wang Xizhi's Preface to the Lanting Pavilion was painted directly or written with thick strokes on the original words.