You can not really do that. As per the WCF specification, every WCF is independent. So, you can not pass data from your first WCF to another. All you have to do it, get response from the first WCF. Create request from the first response and pass on that.
In your scenario, you first enter login and get cookie as you are logged in. After getting cookies, you can either store the session in the memory or db of the server and generate GUID. With second request pass the GUID, retrive the session data where ever it stored and use it.
Hope that answered your question.