How to Paint Faux Flagstone Stepping Stones

Clean the surface of the concrete where you wish to paint the faux flagstones. Sweep away any loose dirt or debris using a push broom and then wash the surface with a pH-neutral cleanser and warm water. Rinse the cleanser off with clean water, because the residue could interfere with the paint. Allow the concrete to dry before proceeding -- let it air-dry or pat the surface dry with a clean cloth.

Remove any sealer from the surface by spreading a layer of concrete sealant remover across it with a squeegee. Allow the remover to sit in place, dissolving the sealant, for the length of time recommended by the manufacturer. Mop off the sealant and the remover with clean water, rinsing the mop often to prevent spreading the thinned sealant farther along the surface. Clean the concrete after removing the sealant with the pH-neutral cleanser again, then rinse and dry a second time before painting.

Create the stamps for your faux flagstones out of the upholstery foam. Tear the foam by hand into rough flagstone shapes, with each stamp between 3 and 10 inches long and in varying widths. Remove any loose material from the face and edges to prevent the pieces from contaminating the paint application.

Paint a grout for your "stones" using an oil-based primer on the concrete. Chose a primer in the color you wish to simulate the grout between stones, and apply the paint to the concrete with a roller. Allow the primer to dry overnight.

Create your stone paint by mixing several oil-based paints to resemble the stone of your choice. Pour a base color into a large paint pan. This is the main color for your stone; use pictures of the stone of your choice as a color guide. Add one or two other colors to the pan, following the picture example for the appropriate minor colors contained in the particular stone type. Add only a small amount of the secondary colors, about one part in 10, as stone accents. Use a paint stick to mix the colors slightly. After mixing, you want your base color to have slight lines and patches of the secondary colors running through.

Apply the paint to the concrete using the foam stamps. Dip the face of the foam into the paint pan, then press it gently onto a piece of newspaper to blot some of the paint. Press the faux-stone stamp onto the concrete to transfer the paint and create your faux flagstone. Take another form, dip it into the paint and press it to the concrete next to the first faux stone, leaving a gap of 3/4 inch between them for the "grout" to show through. Continue in this way, stamping faux flagstones on the concrete until you've covered the entire slab. Rotate the stamps to alter the appearance of the painted stones as you go along for more variety. Allow the paint to cure for 72 hours.

Cover the painted concrete with concrete sealant to protect the surface from the elements. Brush the sealant in place using a squeegee. Allow the sealant to dry for 48 hours before using the surface.