I'm glad to report that my tea professor Teaparker has started a series of articles to teach a few tricks, rules, principles about the technique of gongfu cha. In his first article, he challenges the concept of 'raising' a teapot. Many people in Taiwan (and elsewhere) use a brush to moisten their teapot with tea. Others (or the same) will keep the teapot filled with tea leaves and water overnight to impregnate the teapot with tea. Teaparker reminds us that moisture + organic substance (tea) will transform into mold over time, especially in the humid Asian climate. And a teapot with mold will negatively impact the taste of tea...
In conclusion, he recommends that we pay more attention to have a clean and dry teapot. Rinse it with hot water and let it dry after you have finished drinking your tea. This (functional) principle should comes before the (aesthetic) principle of giving your teapot a glossy shine.
On a related subject, I wrote before about how to prepare a new Yixing teapot.
Note: I have never seen Teaparker using a brush on his teapots. However, he sometimes uses a clean, dry cloth to clean and shine them.