Firstly install Infinite Painter, then open it and press the Brush tool. After it's opened, tap on the + sign and then Create. Now you have to add a name for your brush and customize the style. You can choose from Pencil, Paintbrush, Sprayer, Watercolor, Pen, Marker, Chalk, and Charcoal.
Customize the texture and the the head, then tap on Create. Additionally, you can customize the size of the brush when applied, opacity, flow, spacing, rotation and for the Texture you can customize Style, depth, watercolor, jitter, angle, position, and scaling.