Brush away surface dirt and debris with a bristle brush. Firmly brush the entire surface of the leather, including the places with and without cracks. Brush into the corners.
Wash the surface of the chair with mild soap and warm water. Dampen a clean rag and rub a mild soap solution into the rag, rather than putting the soap directly onto the leather. Wipe the entire surface of the chair. Dry the soap and water with a clean rag.
Dampen a soft cloth with denatured alcohol. Wipe the clean surface of the chair with the alcohol. Before the alcohol dries, wipe it off with a clean, dry rag.
Fill the cracks in the leather using a teaspoon and the filling compound from your leather repair kit. Make sure to get the compound dip into the cracks. Let each filling dry for 15 minutes.
Sand the filler down with 240-grit sandpaper. Rub the sandpaper gently but firmly to wear down the filler and make it level with the chair. Repeat with 400-grit sandpaper.
Apply the repair solution from your leather repair kit with a soft sponge. Wipe a thin layer over the entire surface of the chair. The filler begins to blend in with the original surface of the chair.
Re-inspect the cracks in the leather's surface once the repair solution dries over the filler. Repeat Steps 4 through 6 until satisfied with your result.