To make your own Venetian plaster, you will need to purchase or collect the following items. Buy a large package of premixed joint compound, two shades of paint chosen from the same paint palette (one light and one dark) and two trowels for each person who will be applying the Venetian plaster to the walls. In addition, you will need paint trays, brushes, rollers, clean cotton rags and a disposable bucket. You also will need access to a water faucet.
Scoop about a handful of the premixed joint compound onto the surface of one of your trowels. With your second trowel, scoop small portions of the compound and begin to spread it onto the wall. Spread the compound in different directions and different thicknesses to create intriguing peaks and valleys on the wall.
Continue this process until the entire wall is covered. Smooth out any "peaks" that may be sharp to the touch. Allow the compound to dry for a couple of hours before proceeding.
Choose which of your two colors you want for your base coat, and which you want for the accent shade. Apply the base coat to the entire wall. Start applying the color with a roller, but fill in any spots missed with a paint brush. There will be spots that the roller won't cover due to the texture you've created with the compound. Allow the base coat to dry for one to two hours.
Pour equal parts of your accent paint shade and water into your disposable bucket and mix with a paint stick. Squeeze your cotton rag into a ball shape and dip it into the mixture. Wring out any excess. Dab the color onto the wall, covering as much of the surface as you'd like. You will see the shadowing taking place as you apply this coat. Add as much or little as you want, wiping away any drips with yet another clean rag. The top coat will dry quickly--usually within an hour.