I am a member of two credit unions, both of which participate in the Co-Op Shared ATM network so I can use most credit union ATMs to make withdrawals and deposits. One credit union holds my regular checking account. The other has my mortgage.
Until the automatic payment gets set up, I pay my mortgage by going to a third-credit-union ATM (owned by a CU that is also on the shared ATM network) and withdrawing a pile of cash with one CU's card. I then stick that cash back into the ATM as a deposit with the other CU's card. The payment can thus be made as a "transfer" on the mortgage CU's online banking platform.
It takes minutes to do that versus approximately 3 days to do an account-to-account transfer.