Creative freedom cannot exist without creative control.
Practice
For each object, render it with the tonal, constructive, and occlusion models.
Sphere (to develop control)
Cube (to develop control)
Simple imaginative object, you may use an image for inspiration but do not copy it - create the composition of forms yourself
Craftsmanship
Below are more sophisticated ways to apply tone (value) with acrylic paint - consider utilizing more than one for each rendering model
Dry Brush: dip the tip of one brush (dry) into the paint (without water), wipe off most excess paint, and gently caress the brush circularly onto the canvas like chalk
2-Brush: use one brush (wet) to apply a mixture of water and paint and use the other brush (dry) to massage the mixture circularly across the canvas
Glaze: with one brush (wet) gently drag a mixture of mostly water and less paint over the canvas and allow it to dry (1-2 minutes, or more)
Pre-Mix: (not recommended for our purposes) mix separate tones of paint and apply them accordingly
Tonal Model
Plan your object to be rendered into distinct tonal areas, considering
highlight occurs where light rays make a right angle with the eye
core shadow results from form turning to a point where light rays do not bounce back towards the eye
reflected light occurs from light bouncing off of other surfaces towards the eye
Methodically apply tone to match the shape and brightness of the areas
Ensure that the brightest tone on the dark side is not brighter than the darkest tone on the bright side
Constructive Model
Consider a simplified arrangement of round/flat surfaces to form your object
Apply curves to construct round surfaces and apply lines to construct flat surfaces
If the object contains an intersection, consider emphasizing it with curves/lines from an opposing direction
Occlusion Model
Observe the subtle areas of tonal shifting between and around your object with respect to ambient light (light bouncing infinitely with the environment) instead of a singular directed light
consider why there will not be highlight, core shadow, and reflected light
Methodically apply tone to match the shape and brightness of the areas
Attempt to work within a narrow range of tone to avoid harsh transitions