Importing users/devices?

Sorry if this was answered somewhere else in the message boards, but I can’t find a good way to import a large amount of users/devices without hand importing them using the GUI interface.

Should I use the API functions core_users_add() and core_devices_add() or is there an import tool that has already been written? Is there an order that users/devices should be created in? Are those the only relevant API functions that I need to use?