https://app.steemconnect.com/sign/delegate-vesting-shares?delegatee=ocdb&vesting_shares=1000%20SP

change the "ocdb" part into the current account you're delegating to and put the "1000" to "0", then use the same link and edit the amount after 5 days when you get your undelegation back. Let me know if it worked, haven't tested this link when undelegating but it should work!