How can we use refunded GAS from a transaction in subsequent ETH transfers? In general, how is refunded GAS used? How can we check the status of the amount of refunded GAS?
You don't need to do anything. The gas refund is applied at the end of the transaction, so the total amount of gas your account is charged for already includes the gas refund. (E.g. if the transaction would have cost 50,000 gas but there was a 15,000 gas refund, the transaction costs only 35,000 gas.)