in the same way.. as first advanced custom workflow, create processdefinition.xml, model.xml, message.properties, and add just model.xml n message.properties in custom-model-content.xml and also in web-client-config-custom.xml define the tasks of model..then deploy
same for property file also, add second property file in relevant place. Start the server and deploy 2nd work also will add in advanced workflow. Make sure that name space prefix must be different in both workflows.