I've done it several times & the way I do it is I go through the Ding ressie process, until I get to the payment screen. Then, I cancel my original flight ressie.....The ticketless travel funds are immediately available.....
Then I quickly go back to ding & pay with the ticketless travel funds from the ressie I just cancelled.
It's really simple, you just have to be quick to be sure that you get your flight times