Can this CPFP always ensure that you will be able to alter the parent fees to speed up the transaction? If it works on Electrum, do other wallets adhere to the same consensus?
Child-Pays-for-Parent doesn't actually increase the fee of the parent, it's just the result of current default selection of transactions used by miners.
Here's the PR when it's implemented:
https://github.com/bitcoin/bitcoin/pull/7600What actually happens is the parent and children transaction fees and sizes are all taken into consideration when getting the overall fee rate,
Kind of like a "
bundle deal", you sent a transaction that pays a high fee but it can't be mined unless its parent is mined as well.
So the miners have to check if the overall fee rate when the parent is included is still higher than the other transactions in their mempool.
With that, it's not limited to Electrum, as long as miners use the same transaction selection method, CPFP will work.