Short sales are moving along a little easier than a couple of years ago mainly due to the banks getting better at processing them. That being said the level of success you receive getting your short sale closed lies in the hands of the listing agent that you choose. While today many listing agents take your listing and hand it over to their short sale department, its still very important that the correct things are done to get it sold.
The most important thing in getting the job done in a reasonable amout of time is creating a good relationship with the loss mitigator at the bank and knowing what to say and when and how often to say it. Hand the file to 10 different listing agents and some will get it closed and some will not.
Choosing a good negotiator with good follow up skills is a good start. Even though things are moving faster at the banks these deals must still be pushed through. A good listing agent will always look for different ways to get the job done until its closed.