If you post your request on a DISigner's thread who is currently DISigning, you can assume they will fill it. Once it is complete, most DISigners will post the DISign or a link to DISign on their thread. Some DISigners might PM the DISign to you.
If you start your own thread, most of the time the DISigner will not let you know in advanced if they are going to fill it, so you have to just wait. DISigners tend to prioritize based on when you are leaving, so if you are leaving in 15 months, it may take a while before it is filled. Once it is filled the DISigner will post it (or a link to it) on the same thread you started.
You have to keep track of your requests and the thread you posted your request on. You should check them regularly, because sometimes a DISigner needs clarification before the request can be filled. You don't receive a PM notifying you it is completed.
I hope this helps,
Dee