Using the tutorial I was able to get the AWS_IoT_WiFi example working. Unfortunately the tut/example stops short of showing how to use Device Shadows.
The example sketch uses mqttClient.print() and mqttClient.read() to publish/recieve strings but Device Shadows uses json documents. I've looked at the ArduinoJson library and that looks easy enough. However I don't understand how to publish/receive a json doc. using the ArduinoMqttClient library. Any guidance will be greatly appreciated.