UNDERSTAND THE TECHNIQUE
A flat shape without a straight end
The filbert has a flat belly and a rounded end. This makes a different initial mark from a straight flat brush. It is useful for petals, fruit, cheek areas and other rounded shapes. Start with the full width and observe the edge. Then turn the head slightly onto its side to work more narrowly. Switching between these positions makes the shape more versatile than its name might suggest.
Blending means shaping a transition zone
For this experiment, place two adjacent acrylic colours on the surface and work while both are still wet. Clean the brush and carefully remove excess water so that it does not unintentionally dilute the application. Now touch only the shared boundary with light strokes. The aim is a transition zone in which both colours remain recognisable. Repeatedly crossing the entire area increasingly creates a single mixture. The head itself also fills with paint; clean it periodically if it is only pushing material back and forth.
Open time sets your pace
Acrylic starts to dry at different speeds depending on the layer, room conditions and surface. Once it becomes tacky, further movements can tear the paint film. It is better to continue later with a new layer. Oil often allows more time for transitions, but uninterrupted mixing does not automatically improve the effect there either. With watercolour, the existing moisture in the paper is another decisive factor. A test piece makes this difference visible.
Petals from individual strokes
For a simple petal, touch down lightly with the rounded end, briefly increase the contact area, then lift the head again. This creates a shape with a rounded section and a narrower finish. Vary the direction and leave space between individual petals. Let the brushmark remain visible. Retracing every shape immediately can easily lose the character of the first stroke. Assess the whole flower before adding more details.
Softness is a choice
A painting often benefits from a contrast between distinct and soft edges. Use the filbert selectively at chosen transitions. Not every outline needs to blur. A clear edge can emphasise a focal point; whether a soft edge appears to recede also depends on colour, contrast and subject. Compare two small studies: treat every edge alike in one, and deliberately vary the edges in the other. This teaches you to use the brush as a tool for composition.
All sketches show shape and movement direction schematically. The actual paint mark also depends on paint, surface and moisture.