Let’s play brush painting together! Just use the brushes that come with PS, and let’s make something fun. Don't think of rat paintings as something you dare not touch.
Select the brush tool. Needless to say, everyone knows that there are different built-in brushes in the corresponding brush options.
Preset brushes and brush options, usually in the upper right corner of the software. The various options inside can be understood just by looking at their names, which is very intuitive. It's a very useful thing, I suggest you study it.