According to HGTV, you must apply a base coat, a crackle medium, and then another coat of paint to do a crackle paint technique. The technique requires satin or semi gloss paints, a crackle medium, a paintbrush, a roller or sponges, drop cloths and masking tape. The exact tools used depend on the effect desired and the size of the object painted.
For the crackle paint technique, choose two contrasting colors of paint: a top layer that will crack and a bottom layer to show through. Start by applying the bottom layer of paint with a brush or, if the area is large enough, a roller. Give this bottom layer at least 8 hours to dry completely. Cover any areas you do not want to crackle with masking tape.
Apply the crackle medium over the paint just like another layer of paint. It can be applied with a brush or roller for an all over crackle effect that will tend to follow the brush strokes, or with a sponge for a more sparse, random effect. Allow the medium to dry per the manufacturer's instructions. Finally, apply the top coat of paint quickly and thoroughly, as the crackling will begin immediately once you begin.