1. Deploy your workflow as a webservice. (Workflow Type should be Webservice under Publishing in Project Properties)
2. Run the webservice generator. To do this you can either click the New Integration Library button when a workflow is open, or select Integration library when doing a New project from Workflow Manager - either option goes to the same place. Pick the Web Service generator option.
In the generator, use the URL of the deployed workflow (http://<SERVERNAME>/WorkflowProject1/MyService.asmx, for example) to generate components. Keeping all the defaults is fine. You should be able to generate a component against the Execute method of the webservice.
3. Now that you have an Execute component, you can drop it to any project you want and invoke the workflow as you please.