Hi - have replied in slack, but for those on the list...
here's a simple Slack->Watson Conversation->Slack flow, that uses the node-red-contrib-slacker nodes.
[{"id":"ad1d51dc.312a","type":"slack-in","z":"3eec60d6.58cdd","name":"@iotchatbot","events":"direct_message","controller":"6fa228ce.033678","x":130,"y":620,"wires":[["34d1d5b9.9a6cca"]]},{"id":"34d1d5b9.9a6cca","type":"function","z":"3eec60d6.58cdd","name":"Get user context","func":"var user = msg.user;\n\nvar convContext = flow.get('convContexts')||{};\nconvContext[user] = convContext[user] || {};\nflow.set('convContexts',convContext);\n\nmsg.params = {\n context: convContext[user]\n}\n\n\nreturn msg;","outputs":1,"noerr":0,"x":338,"y":619,"wires":[["5b211cac.d463d4"]]},{"id":"5b211cac.d463d4","type":"watson-conversation-v1","z":"3eec60d6.58cdd","name":"","workspaceid":"","x":518,"y":619,"wires":[["4c58ac48.217704"]]},{"id":"4c58ac48.217704","type":"function","z":"3eec60d6.58cdd","name":"Handle response","func":"var user = msg.user;\nvar convContext = flow.get('convContexts')||{};\n\nconvContext[user] = msg.payload.context;\n\nmsg.payload = msg.payload.output.text.join(\"\\n\");\n\nflow.set('convContexts',convContext);\n\nreturn msg;","outputs":"1","noerr":0,"x":718,"y":619,"wires":[["1c3e064d.e2d4ca"]]},{"id":"1c3e064d.e2d4ca","type":"slack-out","z":"3eec60d6.58cdd","name":"@iotchatbot","channel":"","controller":"6fa228ce.033678","x":910,"y":620,"wires":[]},{"id":"6fa228ce.033678","type":"slack-bot-controller","z":"3eec60d6.58cdd","name":"@iotchatbot","token":""}]