Good question. In most cases even Realtors that claim to know about them are NOT experienced in short sales. However you can certainly put together a questionnaire that will help you identify those that are experienced.
Ask the following questions to an agent:
Do you understand a short sale?
When is the last time you completed a short sale?
Where did you learn about short sales?
Do you have a title company you recommend to close on short sales?
How many total short sales have you completed?
How is the BPO used in a short sale?
That is a good start. You will know pretty quickly which agents to use and which to avoid. Also don’t forget about short sale service companies that work on commission. You will need to Google to find them. I hope this helps.