Wipe down the entire surface of the counter top with warm soapy water. Allow to dry. Dip a rag into white vinegar and wipe down the counter top, removing all spots of grease and grime. Dry the counter top with a clean rag.
Sand the entire counter top with medium-grade sandpaper. Vacuum excess dust from the counter top.
Tape the edges of the walls or cupboards surrounding the counter top with painter's tape. Press the edges of the tape to seal them so paint can't bleed through.
Use the paintbrush to apply a thin coat of oil-based primer to the counter top. Allow to dry. Sand the coat of primer lightly with fine-grade sandpaper. Wipe away all dust with a damp rag. Repeat until you have applied three thin coats of primer.
Use a paintbrush to apply the brown latex paint as the base coat of paint. Allow the paint to dry.
Dip the sponge into the green latex paint. Tap the sponge on the cardboard to remove excess paint. Press the sponge onto the counter top and pull it away. Move the sponge to another spot and press it down again and pull it away. Repeat until the entire counter top has been sponged with the green paint.
Dip the tip of a feather in the black paint. Use the tip of the feather to start painting a wavy line of black paint. Turn the feather sideways and use the side of the feather to paint the line. Then use just the tip again, all in one motion, to make the line wider and narrower as you paint. Lift the feather, dip it in the paint again, and start a new line. Paint wavy lines of black that resemble veins across the counter top in this manner. Allow the black paint to dry.
Use a paint brush to apply a thin coat of urethane to the counter top. Allow to dry. Apply another thin coat.
Remove the painter's tape.