At the moment I don't know which wallet to use. Tell me please which wallet should I use? Which will allow me to send 0.0000004 BTC.
You can try using SafePal wallet from where you can deposit your specified amount of BTC to another address.
Tell me please which wallets support this customizing?
SafePal Wallet, Trustlet supports customization here where you can fully customize the mempool and reduce fees. I will show you through a screenshot so you can try it out.
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Has anyone succeeded in doing this?
Is this feasible what Powerjumboo wrote?