See the Brush Display options.
The Weight Paint Options modify the overall brush behavior:
- This option limits the influence of painting to vertices (even with weight 0) belonging to the selected vertex group.
- X Mirror
- Use the X Mirror option for mirrored painting on groups that have symmetrical names, like with extension «.R»/ «.L» or «_R» / «_L». If a group has no mirrored counterpart, it will paint symmetrically on the active group itself. You can read more about the naming convention in Editing Armatures: Naming conventions. The convention for armatures/bones apply here as well.
- Topology Mirror
- Use topology-based mirroring, for when both sides of a mesh have matching mirrored topology. See here for more information.
- Unified Settings
- The Size, Strength and Weight of the brush can be set to be shared across different brushes, as opposed to per brush.