This a real faux stone because it mimics cut stone and not just a textured surface, which is a common mistake when creating faux stone. This may look ok, but it isn’t realistic. Real, cut stone would be smooth to the touch but pitted (recesses).
To start, a tinted (off-white) primer was applied.
The texture coat consisted of a mixture of SAT (Proceed smooth absorbent texture), RRT (Proceed Rough Regular Texture), and a matte base coat for a chalky, texture.
Apply the texture with a domed glazing brush.
Stipple with a refined tool like a badger 2-header for a small area.
A standard stippler could be used with a light touch, but the smaller brush allows for excellent control over the texture.
Sand with a 220 grit to flatten the peaks so it looks like it has pits and feels smooth to the touch. Don’t over sand. Dust.
A mother glaze was mixed for a cool grey tonality (RawUm, PaynesG, WHITE). The glazing liquid was a mixture of 50% low viscosity glaze, 30% matte medium, and 20% glazing acrylic liquid. The small baseboard sample did not require a glaze with a long open time. Decrease the amount of matte medium or acrylic glazing liquid for a longer open time.
Glaze the surface generously but evenly with a pointed glazing brush.
With a 2 headed flat badger brush, stipple, with enough pressure to melt the tonalities together.
Using a samina chiqueteur, loaded with only water and rung out, texture the surface which will dilute the glaze and create texture by removing the glaze.
Using a spatter brush and a palette knife to create a spatter. Start with RU plus water, then switch to BU, and then an off-white.
Paint grout line with an off white, generally.
Create an illusion of more pits by using a pointed brush with a transparent mix of RU, UB, and white for a cool grey.
Within the pits, add a darker tonality for the shadow on the top part.
Varnish with dead flat.