Mixers are really not needed anymore. If you want to mix your coins, simply register with any exchange, send your coins to them, create a new wallet, and withdraw your coins from the exchange to that wallet. Bam! Your coins are now untraceable.
If we act on the plan proposed by you, it is better to buy XMR to transfer between exchanges... In case of BTC they can trace you anyway... And if you made suspicious purchases in Darknet, then exchanges at least can block your funds...