These are some recent samples I worked up to simulate various surfaces and appearances. This first example is a basic wood grain on a 10 in. x 10 in. panel. I painted the panel with a mixture of gesso and acrylic, mixing some yellow ochre, also some white and raw umber, using the brush to begin suggesting some grain. I then went over the surface in the direction of the grain again using a whisk broom.

Once dry, I painted on a darker glaze using burnt umber, burnt sienna and some black for an extra dark richness. I created the grain using a wood grain rocker tool and finished it with a glossy varnish.

The second example is a rusted but vibrant metal look. Initially I painted the board with some gesso and grays, white and black to give a metal texture underneath. With a spray bottle, I created some droplets, then sprayed some matte black over the drops to leave a textured weathered and greasy effect. 

I began dabbing various warm and cool colors to simulate rust, wear and perhaps some organic or chemical staining effects. I thought about looks that may be appropriate for Galaxy's Edge, Guardians of the Galaxy, or one of my favorite theme park areas: Mysterious Island at Tokyo Disney Sea.

I sprayed some more flat black, some white light spray to create some highlights, and some black washes to create a dingy dripping look.

This third sample is of marble. I used a stock image of Italian granite as reference and worked primarily with three colors: titan buff, yellow ochre and a burnt sienna/umber mix.

I created the striations using a brush, textured with sea sponges, some cheese cloth and rags. I flyspecked these colors with a toothbrush to create more texture.

This white Carrara marble sample is on a 16 in. x 12 in. board. I painted a basecoat of mars black acrylic paint. Once dry, I painted on a pattern of gray and white glaze. I dabbed the surface with crumbled plastic wrap, then flyspecked mineral spirits on the surface to create a fine fossilized appearance. I began adding highlighted areas with a clean piece of balled up plastic wrap dipped in white paint.

To create the veins, I used a feather dipped in white paint and glaze, then in black glaze. I completed the look by flyspecking white and gray glaze, then added a glossy varnish once dry.