Prepare the floor before painting with the concrete paint. Sweep the floor, and allow it to dry if it's wet. Buff the floor to remove glue left by carpet, using medium-grit sandpaper. This also creates a porous surface for the primer. Apply two coats of concrete and masonry primer. Allow the primer to dry for 24 hours. Next, apply the epoxy and let it dry for 24 hours. You can pour the cement paint directly on the floor, or you can cut in around the edges, using a paintbrush, and then fill in the rest of the floor, using a roller. Let this first layer of paint dry for 12 hours. Apply another coat of paint and allow it to dry for seven days. This allows the primer under the paint to continue drying.
Lay out your stencil and line it up with a straightedge, if you purchased a repeating-pattern stencil. Measure out the placement of the design. Mark these lines lightly for easy reference. If this is your first time stenciling, practice by painting the stencil on some cardboard or any smooth, rigid scrap material. You'll get the feel of the paint's texture and the feel of the brush, and you'll also learn how to manipulate the brush.
Tape the stencil in position. Dip the brush in the paint, tap it lightly on a paper towel to get off any excess paint and start applying the paint in a light tapping fashion. Apply the paint to small areas at a time. Clean off the stencil when you're using the same pattern with a different color.
Use separate brushes to apply each color if you're using more than one color. Apply the first color, move the stencil to the next spot and repeat. Once you complete the first round, go back to the beginning. Make sure the first color is dry. Apply the second color, and repeat the process until all the colors are done. Don't pull up the stencil until the paint is dry. If you use fast-drying stencil paints or add Japan Dry to other paints, the paint should be dry when you get back to the beginning.
Apply a coat of nonyellowing polyurethane varnish to the entire floor after you've finished painting your design. Use a paint roller made for varnish and a long extension pole.