If you run through the mixers several times or with several mixers, it is not possible to find out the trace.
I agree with you if the bitcoin is mixed with several mixers the is no how in this world that it will be detected(especially when you mix it little by little amount and send each mixed coin to a different address)
AFTER THAT YOU CAN STILL EXCHANGE TO ALT-COIN THEN BACK TO BITCOIN THEN MIX AGAIN AFTER THAT SPEND IT LITTLE BY LITTLE
REMEMBER TO USE A VPN THAT DON'T KEEP TRACE AND DIFFERENT NON BLACKLISTED SOCKS5 BECAUSE BITCOIN SENT CAN BE TRACED TO AN IP ADDRESS