Draw a curving line length-wise on one sheet of Mylar with the pencil, keeping the curve at least 1-inch from the length-wise edges.
Position leaves on the curved line and trace them on the Mylar with the pencil.
Cut out the curved line and leaves with the craft knife over the cutting board.
Repeat for two more vine and leaf stencil sheets with different curves, matching starting and ending points on each width-wise sheet edge.
Practice dipping the paintbrush in a very small amount of green and brown paint and pressing the paintbrush in the leaf stencil openings over the scrap paper.
Attach the Mylar sheets to the corner wall with the masking tape, using the inside corner edge as a guide.
Dip the paintbrush in a small amount of green and brown paint and press the brush on the leaf and vine openings. Let paint dry before removing Mylar stencil.