Mixers work very well and he can use mixers and the only thing is that mixers are not allowed to advertise their services here but they are advertising it in another platforms or forums. And since he is talking about his privacy to save bitcoin then I also advise him to use mixers to mix his coin to address of his choice. In that way,  nobody will know where the coins go and enter because it is anonymous sending of coins to different addresses at a time. And I don't think Monero network is still active like before again though I am not using it so I can't dwell much on that. But I have used mixers and it was good.