With the Paint Blend Shape Weights Tool, you can use a Maya Artisan brush to paint blend shape weights on your base shapes.
See also What are blend shapes? and Paint blend shape deformer weights.
The Paint Blend Shape Weights Tool menu item is located under the Edit Deformers menu in the Animation menu set ( Edit Deformers > Paint Blend Shape Weights Tool).
Paint Blend Shape Weights Tool Settings
For descriptions of the Paint Blend Shape Weights Tool options common to all Artisan tools (such as those in the Brush, Stroke, and Attribute Maps sections), see Artisan Tool Settings in the Artisan guide.
Paint Operation
The paint operations define how your target shape weights are applied to the base shape.
Sets the minimum and maximum possible paint values. By default, you can paint values between 0 and 1. Setting the Min/Max Values you can extend or narrow the range of values. Negative values are useful for subtracting weight. For example, if you set Min Value to -1, Value to -0.5, and select Add for the operation, you would subtract 0.5 from the weight of vertices you paint. Positive values are used as multipliers.
Clamp
Select whether you want to clamp the values within a specified range, regardless of the Value set when you paint.
Click Flood to apply the brush settings to all the weights on the base shape’s vertices. The result depends on the brush settings defined when you perform the flood. See Flood paint in the Artisan guide.