When it comes to matching textures in plaster, the main rule to keep in mind is that there are no rules. There are special tools for the job, or just use what is on hand. Here are some techniques professionals use:

1. Use a drywall knife to create a skip texture, which looks like sand dunes.

2. A stippling brush is useful for creating heavy texture. Or drag a trowel very lightly across the surface to achieve a knockdown.

3. A stomp brush imparts an interesting deep texture, as does a textured paint roller.

4. Drywall knives and putty knives can be used for a stucco-looking pattern. Vary the direction for a different look, or drag the knife lightly over the top for a smoother surface.

5. Even something as mundane as a whisk broom can be used as a texturing tool.