Is it useful for Shandong calligraphy to pass Band 6?

Of course it works. Calligraphy has passed the grade, which shows that your level is ok. Since your level is good, you can consider becoming a calligraphy teacher.

I guess you also like calligraphy.

Writing calligraphy, in fact, tools are very important

First of all, paper, paper, beginners can use fringed paper.

I think the pen should be the most important,

If you want to buy a writing brush,

I suggest you find this article and read "Top Ten Brush Brands in China (with Brush Selection and Maintenance Methods)".

This paper introduces the selection and maintenance methods of brushes in detail. I hope it helps you.