Marvel mystery oil usually will help things along. Just keep soaking it. You may have shot yourself in the foot by disconnecting everything. The usual method is to soak the cylinders and rock it back and forth using the crank bolt until it frees up. Patience is the key. SOme people have used automatic transmission fluid as well. Where you already have the heads off you can gently tap the tops of the pistons with a hammer and block to help the oil penetrate. You are not trying to move the pistons, just setup a little vibration to help the oil penetrate.