For using async_notify_multiple_devices, you just need to send a list of device push tokens along with a dictionary of paramaters containing your message data. The paramaters closely match the old notify_multiple_devices. Heres the parse function for the message request: def parse_payload( self, fcm_token=None, notification_title=None, notification_body=None, notification_image=None, data_payload=None, topic_name=None, topic_condition=None, android_config=None, apns_config=None, webpush_config=None, fcm_options=None, dry_run=False, ):

So you would send a list of the registration_ids along with a single dictionary containing params like: {"notification_title": "Hi, Im a title", "notification_body":"And Im a body"}