Best way to mix bitcoins? mixer, coin join (shared send), dark wallet, stealth addresses?
I would say connect to tor, create a blockchain.info account, send you bitcoin there, then send the bitcoin to https://shapeshift.io to another currency which you have a wallet setup, then back to a second blockchain account, then to wherever you want.

This is pretty much 100% untraceable, as it goes via anonymous wallet - anonymouswallet - converted to another blockchain, sent to anonymous wallet, then converted back to bitcoin through another anonymous wallet! You can't track that transaction on the blockchain.

Enjoy :)