We will use the Random color technique here there are many different techniques, which are taught at the school in the Encaustic Painting class.
Give the wall a coat of primer and let dry.
Color the Venetian plaster by adding universal tint and mixing well.
Using a trowel, leave random accents of the color of the plaster you would like to see very subtly through the top coat.
Once this is dry, apply the top color thinly over the entire surface and let dry.
Once dry, the color will be a few shades lighter than it is when wet.
Sand the wall in certain areas to let the underlying accents come through very subtly.
Now this is where the real work comes in, take a stainless steel trowel and begin the burnishing of the top coat to bring up the luster of this product.
You can seal the wall with sealing wax for protection (opt.).
There are several encaustic products on the market all of which are sold at the school.