If you don't have an XML dump of devices, but need to do a batch load, just create a file mydevicelist.txt formatted like this:

device0
/Path/To/DeviceClass1
 device1
 device2
 device3
/Path/To/DeviceClass2
 device4
 device5
 device6

Then run:

zenbatchload -i mydevicelist.txt

The script will attempt to discover each device in turn and load it into Zenoss, applying the appropriate device class. If (like device0 in the example) no device class is given, the device will be put into /Discovered. If the device class specified does not exist, it will be created.