Painting needs paint brushes and Blender provides a Brush panel within the Toolbar when in Weight Paint Mode.
In the Data-Block menu you find predefined Brush presets. And you can create your own custom presets as needed.
This option controls the radius of the brush, measured in pixels. F allows you to change the brush size interactively by dragging the mouse and then LMB (the texture of the brush should be visible inside the circle). Typing a number then enter while using F allows you to enter the size numerically.
Brush size can be affected by enabling the pressure sensitivity icon, if you are using a Graphics Tablet.
How powerful the brush is when applied.
Strength can be affected by enabling the pressure sensitivity icon, if you are using a Graphics Tablet.
Only paint over strokes.
Only paint over fill areas.
- Stroke and Fill
Paint over strokes and fill areas.
See the global brush settings for Cursor settings.
The color of the brush. See Color Picker.
Note that Vertex Paint works in sRGB space and the RGB representation of the same colors will be different between the paint tools and the materials that are in linear space.