There is no need to send more coins to A2. That does not "replenish" anything. Here is how it is done, assuming coins were sent from A1 to A2, but the amount of the transaction fee was too low:


1. Send the entire balance of A2 (including the unconfirmed transaction) to an address in your wallet (A4), and pay a transaction fee that is enough to pay for both the A1→A2 and A2→A4 transactions.


There may be a complication. Some wallets don't allow you to send unconfirmed coins and CPFP does just that. The solution is to look in you wallet settings for an option to send unconfirmed coins and enable it just for this transaction.

Generally, you use CPFP when you are the receiver of the coins because you must control A2. However, if you don't control A2, you may still be able to use CPFP. When you send from A1 to A2 and the amount in A1 is greater than A2, then the remainder will be sent to a change address (C) in your wallet. It looks like this:

A1 → A2 + C

In this case:


1. Send the balance of C (including the unconfirmed transaction) to an address in your wallet (A4), and pay a transaction fee that is enough to pay for both the A1→A2+C and C→A4 transactions.



Also, sending from a specific address may require something called coin control, which is an advanced feature. If you don't want to use coin control just do this:


1. Send the entire balance of your wallet (including the unconfirmed change) to an address in your wallet (A4), and pay a transaction fee that is enough to pay for both the A1→A2 and everything→A4 transactions.