Sometimes the most difficult part of repairing stress cracks in drywall is matching the existing texture. There are spray cans for many common textures which make it easier to hide repairs, but other textures need to be done by hand. Crows foot (also called stomp or slap brush) texture is applied with a roller and special texturing brush, using watered-down joint compound. The brushes are available anywhere drywall supplies are sold, and with a little practice it's easy to learn a crows foot texture technique.
Remove loose drywall material from the stress cracks with the edge of a putty knife.
Push on the surface surrounding the crack. If the wall flexes or gives, secure it to the underlying wall studs or ceiling joists with drywall screws.
Apply a strip of fibreglass mesh drywall tape along the crack. It's sticky on one side, so press it securely over the crows foot texture.
Apply two or three coats of joint compound over the crack, using a six- or nine-inch drywall knife. Don't sand in between the coats--if there are ridges, knock them flat with the drywall knife. Sand the final coat until it's level with the surrounding surface.
Mix joint compound with water in a five-gallon bucket until the joint compound is about the consistency of mayonnaise.
Roll the thinned joint compound over the repair using a one-inch lambswool roller cover. If the repair area is small, you can brush on a heavy coat of joint compound. Extend the wet mixture beyond the boundaries of the repair to give yourself room to blend the crows foot texture with the existing surface.
Slap the texture brush into the wet joint compound, then pull it away from the surface. Rotate the brush a little and slap it again. Continue until the texture is uniform.
Allow it to dry for about eight hours, or until it has turned from grey to white, before priming and painting.
There are several styles of crows foot or stomp texture brushes. It will help if you can take a clear photo of the existing texture, and bring it to the building supply store so staff can tell you which one will work best. Practice on a spare piece of cardboard or plywood first to get a feel for the technique.