Adding water seems to be useful, but it is actually too much. When the ink on the paper dries, the paper will become warped. I haven't found a better way. Online methods are too annoying. The simple way is to take a cabinet ink 1 and a Beijing ink 4. However, I don't know whether it's good or not, so this is a way. Now the ink is too heavy, and calligraphy is not easy to use.
The most direct way is to buy varnish ink.