The use of brush application is becoming less common for topcoat work, because of its time consuming application and slow drying, but is commonly used for polyester or hi-build fillers on poor panel repairs or filler work, where the brush marks need blocking out prior to colour. Material applied by brush must be well brushed out and 'laid off' at 90°. The finer the hair, the less intrusion will be the brush marks. Avoid uneven coating and unnecessary build-up of material. The brushes must be washed out thoroughly and not left in solvent.