Failure of paint to dry to a smooth film, resulting in unsightly brush and roller marks after the paint dries.
Use of lower quality paint
Application of additional paint to 'touch up' partially dried painted areas
Re-brushing or re-rolling partially dried painted areas
Use of the incorrect application equipment (e.g. wrong type of roller cover or poor quality brush)
Use premium quality water-based paints, which are generally formulated with ingredients that enhance paint flow. Brush and roller marks thus tend to 'flow out' and form a smooth film.
When using a roller, be sure to use a cover with the recommended nap length for the type of paint being used. Use of a high quality brush is important as a poor brush will impact on the overall appearance.