personally,I would take your little dog to where rats are out feeding at night,encourage the rats to feed away from holes by dumping grain amongst bags,logs,small bales, any thing you can move easily.Do this for a few nights prior to your hunt and on the night, make sure you aproach the area quietly.If your dog has anything about it, and rats are where youve fed them to ,he will mark like crazy.Move some kit to where the dog marks,rat out,dog catches rat ,rat bites dog,dog shakes rat and bingo.Failing all the above, buy a rat from apet shop!.