UNDERSTAND THE TECHNIQUE
Get to know the short flat shape
The Fleury film describes the Chisel Blender as having a straight edge and shorter fibres than a regular flat brush. It mentions controlled application, blending, thin lines and hard edges with acrylic. Use the broad side for a small area and the narrow edge for a finer mark. This does not specify fixed coverage per load or a measurable advantage in control. For your own work, compare a short stroke with the Chisel Blender and one with a longer flat brush of similar width.
Distinguish opaque application from blending
For a distinct acrylic accent, load the head appropriately and make a deliberate stroke. For blending, it should introduce hardly any extra paint. Clean it, remove excess moisture and touch the transition zone with light pressure. The same movement has a different effect depending on the load. Practise both states side by side. This helps you see whether you are applying paint, spreading it or carrying it from one place to another.
A crisp edge as a visual accent
Place the straight end along a small shape and pull only as far as the paint load allows a clean application. A short, distinct edge can emphasise a highlight, an object's edge or a geometric section. If you need to refine a corner, take a little paint and realign the head. Frequent scrubbing with the entire head enlarges the area being worked and can lose the original precision of the accent.
Distinguish fresh and dry acrylic paint
Direct blending requires acrylic colours that are still workable. Once a layer becomes tacky, further movements can create visible joins or disturb the application. Let it dry at that point. On a dry acrylic layer, new paint creates another application; a soft transition must be shaped afresh. This is a different step from mixing two wet areas of colour. Check the state with a small test beside the subject rather than trying to force a transition with increasing pressure.
Preserve the shape through care
Paint that reaches the base near the ferrule and dries there can spread the fibres. Load only as deeply as necessary, and clean the head regularly during longer sessions using a method suited to the medium. Do not force it against the bottom of a container. Gently reshape the clean head and let it dry without pressure on it. A clean edge is the foundation for a controlled short stroke next time.
All sketches show shape and movement direction schematically. The actual paint mark also depends on paint, surface and moisture.