Although the luminance of the object is created when adding the blob model base in the beginning of the process, highlights and shadows can be adjusted at any time.

Use the Blob Shadow and the Blob Highlight brushes to adjust the model luminance.

The Opacity slider here will control the shading strength.

When adjusting the object luminance, in addition to the Blob Highlight and Blob Shadow brushes included in the Blob Studio ArtSet, a number of different texture brushes can be used. These brushes can be found in the Blob Studio - Texture ArtSet and will add highlights and shadows of different textures to your model.