He probably used mixers and coinjoin transactions which are going to require advanced software
Does this mean that even a coin is mixed then it still can be track? Back in the day, I know that many people use bitcoin gambling website such as primedice and justdice to launder because there are so many incoming deposit and withdrawals there and your coins will never be trackable. He could be using bitmixer and I never heard someone track a coin after it is mix by bitmixer