Put down a drop cloth to protect your work area.
Sand along the frieze’s raised portions using 100-grit sandpaper, if it is a frieze that uses bas relief. Every raised surface, especially at eye level and below, should have at least a small amount of wear.
Sand highlights into the frieze. Look at spots that you want to make more visible or to stand out and lightly sand them using 100-grit sandpaper. Try not to go all the way through to the plaster, but if you do, do so only once or twice.
Wipe away any dust that has accumulated with a clean cloth or vacuum the dust out of the frieze with a crevice attachment.
Wet a clean cloth with water and use it to rub down the areas that you have sanded. This makes the distressing look less deliberate and it also gives your frieze a soft glow. Once the frieze dries, you can seal the frieze or simply leave it as is.