Brush marks in dry paint film are often due to poor quality applicators. If the polyester or nylon filament of a brush is not finished properly, it will leave marks. Other causes include a too-porous surface that absorbs too much coating, excessive brushing, applying too little paint, using the wrong type thinner or not allowing enough drying time between coats. Brush marks will also occur in paint films that dry too rapidly.

SOLUTION: Always use top quality applicators. Brushes should contain tapered bristles properly flagged and tipped.

Smooth the surface by sanding before repainting, or the brush marks will show through the new coat. If the surface is porous a primer should be applied before painting. Be sure to use a recommended thinner if the coating is too thick and allow the paint to dry completely between coats.