Crack cured walnuts after preconditioning, according to the University of Illinois Homeowner's Column. Soak walnuts in water for two hours, and then store in an airtight container overnight. Position nuts on a hard surface with points upward and tap with a mallet. Hand-separate the shells from the kernel.
If the shell is still brittle before separating, soak for a moment in hot tap water. For best results, the University of Illinois Homeowners Column recommends allowing the nutmeat to dry for a day before eating or storing in a fridge or freezer. Frozen nutmeat can keep for two years or more.