What brush should I use to practice regular script?

Wool.

Beginners of calligraphy must use wool, which is soft and can be used to practice brushwork. This view seems reasonable, but it is groundless. According to textual research, writing with wool became popular only after the Southern Song Dynasty. But it was widely used after the early Qing Dynasty. "Because the Qing Dynasty paid attention to roundness and delicacy and was not allowed to show off talents, only soft wool could meet the requirements and was widely used at that time." Until now, bristles.

Extended data:

According to legend, Wang Xizhi probably wrote Preface to the Lanting Pavilion with a moustache (although what a moustache is remains to be verified, at least it shows that he used a hard brush). In addition, "a soft brush may not be able to practice writing ability, and writing ability depends on active exertion, while too soft wool is easy to develop the bad habit of dragging pens, which is not conducive to the cultivation of active exertion habits."

Don't use a pointed brush. If the long front brush is made of animal hair, the cost is extremely high. Before Qi Ming, when I visited Mr. Ye Keqin of Yantian Academy, I saw some of his best long-feng sheep brushes, which were about 6 cm long. The output of this long-front wool brush is very low, and sometimes it takes months or even more than a year to save enough wool for this brush. The same is true of wolf hair and purple hair. The longer it is, the more expensive it is.