We have had to do this with a CRJ before. You just need to plan ahead and have the area around the a/c secured.
Procedure is: Shut down #2 to disembark and unload luggage. Restart #2 and shut down #1 to refuel. Restart #1 and shut down #2 to embark and load luggage.
You must have safety guys at aircraft to secure area and fire brigade in attendance is a very good idea. Obviously pilots must be in cockpit and have comms with people outside.
We did not dispatch with u/s APU. It would not start on arrival.