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If you're OK with creating an extra wallet, you can transfer your bitcoins to Samourai Wallet, which has a whirlpool mixing feature based off of Coinjoin (a many-input, many-output featuring inputs from multiple users and outputs going to multiple users), and then you can transfer the bitcoins from Samourai wallet back to your own wallet.
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I didn't know about this wallet, sounds very interesting: can you tell me something in more detail about the effectiveness of its mixing technique? Is it possible to spread the outputs over time like mixing services do?