Much of the Same thing that you did before.
I mean don't include use cases. I will hire you again at the end of the month to do those.
But fill in as much details as possible to every section. But you do not have to indulge in the complications of the design document... i mean don't answer the minuscule questions, that way you will be able to do better time management. Just leave them open! You can probably easily use the material that you wrote before to fill in the blanks, even the security, appendix etc sections that were not defined before! But for the other sections that you had already wrote, just utilize the old material if you think it still pertains.
I need it get done asap.
Let me know if you have time & would be able to get it done within 48 Hours.
And how much would you charge for it. Because of the short deadline, Please do respond soon as if you are not interested, I can look for other people to get this done.