Spread a painter’s tarp on the floor before beginning work on the taped wall.
Spread approximately 1/4 inch of drywall mud on the wall.
Start at one side of the wall next to the ceiling and press the flat side of the trowel against the drywall mud. Pull the trowel out from the mud to form raised peaks.
Use the flat side of the trowel to lightly smooth the peaks to form the stone-like texture you desire.
Use a pencil eraser to carve the outlines of individual stones in the drywall while it is still wet. Push the eraser approximately halfway into the plaster's depth to form the lines between the stones.
Allow the wall to dry for 48 hours before painting.
Use a narrow paintbrush to apply grout-colored latex paint to the lines you inscribed into the drywall, allow it to dry and then paint a second coat into the lines.
Apply one light coat of paint to the wall by softly passing a paint roller over it and allowing it to dry.
Spread a stone-colored glaze over the wall with a large sponge and then immediately blot off the excess with a cloth.